Merge branch 'submodupdate'

6 files changed, 478 insertions, 295 deletions

diff --git a/doc/source/changes.rst b/doc/source/changes.rst
index d820c8ca..74692955 100644
--- a/doc/source/changes.rst
+++ b/doc/source/changes.rst
@@ -21,15 +21,11 @@ Changelog
  
   * ``create(...)`` method now supports the reflog, but will not raise ``GitCommandError`` anymore as it is a pure python implementation now. Instead, it raises ``OSError``.
   
- * **Intrusive Changes** to ``Actor`` type
- 
-  * the *name* field is now using unicode if ascii does not match
-  
  * **Intrusive Changes** to ``Repo`` type
  
-  * ``create_head(...)`` method does not support **kwargs anymore, instead it supports a logmsg parameter
+  * ``create_head(...)`` method does not support kwargs anymore, instead it supports a logmsg parameter
      
-* Repo.rev_parse now supports the [ref]@{n} syntax, where n is the number of steps to look into the reference's past
+* Repo.rev_parse now supports the [ref]@{n} syntax, where *n* is the number of steps to look into the reference's past
 
 * **BugFixes**
 
diff --git a/objects/submodule/base.py b/objects/submodule/base.py
index 36b48d78..88cc42da 100644
--- a/objects/submodule/base.py
+++ b/objects/submodule/base.py
@@ -12,7 +12,8 @@ from StringIO import StringIO					# need a dict to set bloody .name field
 from git.util import (
 						Iterable, 
 						join_path_native, 
-						to_native_path_linux
+						to_native_path_linux,
+						RemoteProgress
 					)
 
 from git.config import SectionConstraint
@@ -20,6 +21,7 @@ from git.exc import (
 					InvalidGitRepositoryError, 
 					NoSuchPathError
 					)
+
 import stat
 import git
 
@@ -29,7 +31,23 @@ import time
 
 import shutil
 
-__all__ = ["Submodule"]
+__all__ = ["Submodule", "UpdateProgress"]
+
+
+class UpdateProgress(RemoteProgress):
+	"""Class providing detailed progress information to the caller who should 
+	derive from it and implement the ``update(...)`` message"""
+	CLONE, FETCH, UPDWKTREE = [1 << x for x in range(RemoteProgress._num_op_codes, RemoteProgress._num_op_codes+3)]
+	_num_op_codes = RemoteProgress._num_op_codes + 3
+	
+	__slots__ = tuple()
+	
+	
+BEGIN = UpdateProgress.BEGIN
+END = UpdateProgress.END
+CLONE = UpdateProgress.CLONE
+FETCH = UpdateProgress.FETCH
+UPDWKTREE = UpdateProgress.UPDWKTREE
 
 
 # IndexObject comes via util module, its a 'hacky' fix thanks to pythons import 
@@ -285,7 +303,8 @@ class Submodule(util.IndexObject, Iterable, Traversable):
 		
 		return sm
 		
-	def update(self, recursive=False, init=True, to_latest_revision=False):
+	def update(self, recursive=False, init=True, to_latest_revision=False, progress=None, 
+				dry_run=False):
 		"""Update the repository of this submodule to point to the checkout
 		we point at with the binsha of this instance.
 		
@@ -297,6 +316,9 @@ class Submodule(util.IndexObject, Iterable, Traversable):
 			This only works if we have a local tracking branch, which is the case
 			if the remote repository had a master branch, or of the 'branch' option 
 			was specified for this submodule and the branch existed remotely
+		:param progress: UpdateProgress instance or None of no progress should be shown
+		:param dry_run: if True, the operation will only be simulated, but not performed.
+			All performed operations are read-only
 		:note: does nothing in bare repositories
 		:note: method is definitely not atomic if recurisve is True
 		:return: self"""
@@ -304,13 +326,41 @@ class Submodule(util.IndexObject, Iterable, Traversable):
 			return self
 		#END pass in bare mode
 		
+		if progress is None:
+			progress = UpdateProgress()
+		#END handle progress
+		prefix = ''
+		if dry_run:
+			prefix = "DRY-RUN: "
+		#END handle prefix
+		
+		# to keep things plausible in dry-run mode
+		if dry_run:
+			mrepo = None
+		#END init mrepo
 		
 		# ASSURE REPO IS PRESENT AND UPTODATE
 		#####################################
 		try:
 			mrepo = self.module()
-			for remote in mrepo.remotes:
-				remote.fetch()
+			rmts = mrepo.remotes
+			len_rmts = len(rmts)
+			for i, remote in enumerate(rmts):
+				op = FETCH
+				if i == 0:
+					op |= BEGIN
+				#END handle start
+				
+				progress.update(op, i, len_rmts, prefix+"Fetching remote %s of submodule %r" % (remote, self.name))
+				#===============================
+				if not dry_run:
+					remote.fetch(progress=progress)
+				#END handle dry-run
+				#===============================
+				if i == len_rmts-1:
+					op |= END
+				#END handle end
+				progress.update(op, i, len_rmts, prefix+"Done fetching remote of submodule %r" % self.name)
 			#END fetch new data
 		except InvalidGitRepositoryError:
 			if not init:
@@ -320,7 +370,7 @@ class Submodule(util.IndexObject, Iterable, Traversable):
 			
 			# there is no git-repository yet - but delete empty paths
 			module_path = join_path_native(self.repo.working_tree_dir, self.path)
-			if os.path.isdir(module_path):
+			if not dry_run and os.path.isdir(module_path):
 				try:
 					os.rmdir(module_path)
 				except OSError:
@@ -330,31 +380,38 @@ class Submodule(util.IndexObject, Iterable, Traversable):
 			
 			# don't check it out at first - nonetheless it will create a local
 			# branch according to the remote-HEAD if possible
-			mrepo = git.Repo.clone_from(self.url, module_path, n=True)
+			progress.update(BEGIN|CLONE, 0, 1, prefix+"Cloning %s to %s in submodule %r" % (self.url, module_path, self.name))
+			if not dry_run:
+				mrepo = git.Repo.clone_from(self.url, module_path, n=True)
+			#END handle dry-run
+			progress.update(END|CLONE, 0, 1, prefix+"Done cloning to %s" % module_path)
 			
-			# see whether we have a valid branch to checkout
-			try:
-				# find  a remote which has our branch - we try to be flexible
-				remote_branch = find_first_remote_branch(mrepo.remotes, self.branch_name)
-				local_branch = mkhead(mrepo, self.branch_path)
-				
-				# have a valid branch, but no checkout - make sure we can figure
-				# that out by marking the commit with a null_sha
-				local_branch.set_object(util.Object(mrepo, self.NULL_BIN_SHA))
-				# END initial checkout + branch creation
-				
-				# make sure HEAD is not detached
-				mrepo.head.set_reference(local_branch, logmsg="submodule: attaching head to %s" % local_branch)
-				mrepo.head.ref.set_tracking_branch(remote_branch)
-			except IndexError:
-				print >> sys.stderr, "Warning: Failed to checkout tracking branch %s" % self.branch_path 
-			#END handle tracking branch
 			
-			# NOTE: Have to write the repo config file as well, otherwise
-			# the default implementation will be offended and not update the repository
-			# Maybe this is a good way to assure it doesn't get into our way, but 
-			# we want to stay backwards compatible too ... . Its so redundant !
-			self.repo.config_writer().set_value(sm_section(self.name), 'url', self.url)
+			if not dry_run:
+				# see whether we have a valid branch to checkout
+				try:
+					# find  a remote which has our branch - we try to be flexible
+					remote_branch = find_first_remote_branch(mrepo.remotes, self.branch_name)
+					local_branch = mkhead(mrepo, self.branch_path)
+					
+					# have a valid branch, but no checkout - make sure we can figure
+					# that out by marking the commit with a null_sha
+					local_branch.set_object(util.Object(mrepo, self.NULL_BIN_SHA))
+					# END initial checkout + branch creation
+					
+					# make sure HEAD is not detached
+					mrepo.head.set_reference(local_branch, logmsg="submodule: attaching head to %s" % local_branch)
+					mrepo.head.ref.set_tracking_branch(remote_branch)
+				except IndexError:
+					print >> sys.stderr, "Warning: Failed to checkout tracking branch %s" % self.branch_path 
+				#END handle tracking branch
+				
+				# NOTE: Have to write the repo config file as well, otherwise
+				# the default implementation will be offended and not update the repository
+				# Maybe this is a good way to assure it doesn't get into our way, but 
+				# we want to stay backwards compatible too ... . Its so redundant !
+				self.repo.config_writer().set_value(sm_section(self.name), 'url', self.url)
+			#END handle dry_run
 		#END handle initalization
 		
 		
@@ -362,8 +419,12 @@ class Submodule(util.IndexObject, Iterable, Traversable):
 		############################
 		binsha = self.binsha
 		hexsha = self.hexsha
-		is_detached = mrepo.head.is_detached
-		if to_latest_revision:
+		if mrepo is not None:
+			# mrepo is only set if we are not in dry-run mode or if the module existed
+			is_detached = mrepo.head.is_detached
+		#END handle dry_run
+		
+		if not dry_run and to_latest_revision:
 			msg_base = "Cannot update to latest revision in repository at %r as " % mrepo.working_dir
 			if not is_detached:
 				rref = mrepo.head.ref.tracking_branch()
@@ -380,27 +441,35 @@ class Submodule(util.IndexObject, Iterable, Traversable):
 		# END handle to_latest_revision option
 		
 		# update the working tree
-		if mrepo.head.commit.binsha != binsha:
-			if is_detached:
-				# NOTE: for now we force, the user is no supposed to change detached
-				# submodules anyway. Maybe at some point this becomes an option, to 
-				# properly handle user modifications - see below for future options
-				# regarding rebase and merge.
-				mrepo.git.checkout(hexsha, force=True)
-			else:
-				# TODO: allow to specify a rebase, merge, or reset
-				# TODO: Warn if the hexsha forces the tracking branch off the remote
-				# branch - this should be prevented when setting the branch option
-				mrepo.head.reset(hexsha, index=True, working_tree=True)
-			# END handle checkout
+		# handles dry_run
+		if mrepo is not None and mrepo.head.commit.binsha != binsha:
+			progress.update(BEGIN|UPDWKTREE, 0, 1, prefix+"Updating working tree at %s for submodule %r" % (self.path, self.name))
+			if not dry_run:
+				if is_detached:
+					# NOTE: for now we force, the user is no supposed to change detached
+					# submodules anyway. Maybe at some point this becomes an option, to 
+					# properly handle user modifications - see below for future options
+					# regarding rebase and merge.
+					mrepo.git.checkout(hexsha, force=True)
+				else:
+					# TODO: allow to specify a rebase, merge, or reset
+					# TODO: Warn if the hexsha forces the tracking branch off the remote
+					# branch - this should be prevented when setting the branch option
+					mrepo.head.reset(hexsha, index=True, working_tree=True)
+				# END handle checkout
+			#END handle dry_run
+			progress.update(END|UPDWKTREE, 0, 1, prefix+"Done updating working tree for submodule %r" % self.name)
 		# END update to new commit only if needed
 		
 		# HANDLE RECURSION
 		##################
 		if recursive:
-			for submodule in self.iter_items(self.module()):
-				submodule.update(recursive, init, to_latest_revision)
-			# END handle recursive update
+			# in dry_run mode, the module might not exist
+			if mrepo is not None:
+				for submodule in self.iter_items(self.module()):
+					submodule.update(recursive, init, to_latest_revision, progress=progress, dry_run=dry_run)
+				# END handle recursive update
+			#END handle dry run
 		# END for each submodule
 			
 		return self
@@ -800,8 +869,7 @@ class Submodule(util.IndexObject, Iterable, Traversable):
 	def children(self):
 		"""
 		:return: IterableList(Submodule, ...) an iterable list of submodules instances
-			which are children of this submodule
-		:raise InvalidGitRepositoryError: if the submodule is not checked-out"""
+			which are children of this submodule or 0 if the submodule is not checked out"""
 		return self._get_intermediate_items(self)
 		
 	#} END query interface
diff --git a/objects/submodule/root.py b/objects/submodule/root.py
index 753c6df4..36cd7209 100644
--- a/objects/submodule/root.py
+++ b/objects/submodule/root.py
@@ -1,4 +1,4 @@
-from base import Submodule
+from base import Submodule, UpdateProgress
 from util import (
 					find_first_remote_branch
 				)
@@ -7,9 +7,23 @@ import git
 
 import sys
 
-__all__ = ["RootModule"]
+__all__ = ["RootModule", "RootUpdateProgress"]
 
+
+class RootUpdateProgress(UpdateProgress):
+	"""Utility class which adds more opcodes to the UpdateProgress"""
+	REMOVE, PATHCHANGE, BRANCHCHANGE, URLCHANGE = [1 << x for x in range(UpdateProgress._num_op_codes, UpdateProgress._num_op_codes+4)]
+	_num_op_codes = UpdateProgress._num_op_codes+4
 	
+	__slots__ = tuple()
+
+BEGIN = RootUpdateProgress.BEGIN
+END = RootUpdateProgress.END
+REMOVE = RootUpdateProgress.REMOVE
+BRANCHCHANGE = RootUpdateProgress.BRANCHCHANGE
+URLCHANGE = RootUpdateProgress.URLCHANGE
+PATHCHANGE = RootUpdateProgress.PATHCHANGE
+
 class RootModule(Submodule):
 	"""A (virtual) Root of all submodules in the given repository. It can be used
 	to more easily traverse all submodules of the master repository"""
@@ -38,7 +52,8 @@ class RootModule(Submodule):
 	
 	#{ Interface 
 	
-	def update(self, previous_commit=None, recursive=True, force_remove=False, init=True, to_latest_revision=False):
+	def update(self, previous_commit=None, recursive=True, force_remove=False, init=True, 
+					to_latest_revision=False, progress=None, dry_run=False):
 		"""Update the submodules of this repository to the current HEAD commit.
 		This method behaves smartly by determining changes of the path of a submodules
 		repository, next to changes to the to-be-checked-out commit or the branch to be 
@@ -57,15 +72,26 @@ class RootModule(Submodule):
 		:param init: If we encounter a new module which would need to be initialized, then do it.
 		:param to_latest_revision: If True, instead of checking out the revision pointed to 
 			by this submodule's sha, the checked out tracking branch will be merged with the 
-			newest remote branch fetched from the repository's origin"""
+			newest remote branch fetched from the repository's origin
+		:param progress: RootUpdateProgress instance or None if no progress should be sent
+		:param dry_run: if True, operations will not actually be performed. Progress messages
+			will change accordingly to indicate the WOULD DO state of the operation."""
 		if self.repo.bare:
 			raise InvalidGitRepositoryError("Cannot update submodules in bare repositories")
 		# END handle bare
 		
+		if progress is None:
+			progress = RootUpdateProgress()
+		#END assure progress is set
+		
+		prefix = ''
+		if dry_run:
+			prefix = 'DRY-RUN: '
+		
 		repo = self.repo
 		
-		# HANDLE COMMITS
-		##################
+		# SETUP BASE COMMIT
+		###################
 		cur_commit = repo.head.commit
 		if previous_commit is None:
 			try:
@@ -89,28 +115,51 @@ class RootModule(Submodule):
 		
 		# HANDLE REMOVALS
 		###################
-		for rsm in (spsms - ssms):
+		rrsm = (spsms - ssms)
+		len_rrsm = len(rrsm)
+		for i, rsm in enumerate(rrsm):
+			op = REMOVE
+			if i == 0:
+				op |= BEGIN
+			#END handle begin
+			
 			# fake it into thinking its at the current commit to allow deletion
 			# of previous module. Trigger the cache to be updated before that
-			#rsm.url
+			progress.update(op, i, len_rrsm, prefix+"Removing submodule %r at %s" % (rsm.name, rsm.abspath))
 			rsm._parent_commit = repo.head.commit
-			rsm.remove(configuration=False, module=True, force=force_remove)
+			if not dry_run:
+				rsm.remove(configuration=False, module=True, force=force_remove)
+			#END handle dry-run
+			
+			if i == len_rrsm-1:
+				op |= END
+			#END handle end
+			progress.update(op, i, len_rrsm, prefix+"Done removing submodule %r" % rsm.name)
 		# END for each removed submodule
 		
 		# HANDLE PATH RENAMES
 		#####################
 		# url changes + branch changes
-		for csm in (spsms & ssms):
+		csms = (spsms & ssms)
+		len_csms = len(csms)
+		for i, csm in enumerate(csms):
 			psm = psms[csm.name]
 			sm = sms[csm.name]
 			
+			#PATH CHANGES
+			##############
 			if sm.path != psm.path and psm.module_exists():
+				progress.update(BEGIN|PATHCHANGE, i, len_csms, prefix+"Moving repository of submodule %r from %s to %s" % (sm.name, psm.abspath, sm.abspath))  
 				# move the module to the new path
-				psm.move(sm.path, module=True, configuration=False)
+				if not dry_run:
+					psm.move(sm.path, module=True, configuration=False)
+				#END handle dry_run
+				progress.update(END|PATHCHANGE, i, len_csms, prefix+"Done moving repository of submodule %r" % sm.name)
 			# END handle path changes
 			
 			if sm.module_exists():
-				# handle url change
+				# HANDLE URL CHANGE
+				###################
 				if sm.url != psm.url:
 					# Add the new remote, remove the old one
 					# This way, if the url just changes, the commits will not 
@@ -121,111 +170,119 @@ class RootModule(Submodule):
 					
 					# don't do anything if we already have the url we search in place
 					if len([r for r in rmts if r.url == sm.url]) == 0:
+						progress.update(BEGIN|URLCHANGE, i, len_csms, prefix+"Changing url of submodule %r from %s to %s" % (sm.name, psm.url, sm.url))
 						
-						
-						assert nn not in [r.name for r in rmts]
-						smr = smm.create_remote(nn, sm.url)
-						smr.fetch()
-						
-						# If we have a tracking branch, it should be available
-						# in the new remote as well.
-						if len([r for r in smr.refs if r.remote_head == sm.branch_name]) == 0:
-							raise ValueError("Submodule branch named %r was not available in new submodule remote at %r" % (sm.branch_name, sm.url))
-						# END head is not detached
-						
-						# now delete the changed one
-						rmt_for_deletion = None
-						for remote in rmts:
-							if remote.url == psm.url:
-								rmt_for_deletion = remote
-								break
-							# END if urls match
-						# END for each remote
-						
-						# if we didn't find a matching remote, but have exactly one, 
-						# we can safely use this one
-						if rmt_for_deletion is None:
-							if len(rmts) == 1:
-								rmt_for_deletion = rmts[0]
-							else:
-								# if we have not found any remote with the original url
-								# we may not have a name. This is a special case, 
-								# and its okay to fail here
-								# Alternatively we could just generate a unique name and leave all
-								# existing ones in place
-								raise InvalidGitRepositoryError("Couldn't find original remote-repo at url %r" % psm.url)
-							#END handle one single remote
-						# END handle check we found a remote
-						
-						orig_name = rmt_for_deletion.name
-						smm.delete_remote(rmt_for_deletion)
-						# NOTE: Currently we leave tags from the deleted remotes
-						# as well as separate tracking branches in the possibly totally 
-						# changed repository ( someone could have changed the url to 
-						# another project ). At some point, one might want to clean
-						# it up, but the danger is high to remove stuff the user
-						# has added explicitly
-						
-						# rename the new remote back to what it was
-						smr.rename(orig_name)
-						
-						# early on, we verified that the our current tracking branch
-						# exists in the remote. Now we have to assure that the 
-						# sha we point to is still contained in the new remote
-						# tracking branch.
-						smsha = sm.binsha
-						found = False
-						rref = smr.refs[self.branch_name]
-						for c in rref.commit.traverse():
-							if c.binsha == smsha:
-								found = True
-								break
-							# END traverse all commits in search for sha
-						# END for each commit
-						
-						if not found:
-							# adjust our internal binsha to use the one of the remote
-							# this way, it will be checked out in the next step
-							# This will change the submodule relative to us, so 
-							# the user will be able to commit the change easily
-							print >> sys.stderr, "WARNING: Current sha %s was not contained in the tracking branch at the new remote, setting it the the remote's tracking branch" % sm.hexsha
-							sm.binsha = rref.commit.binsha
-						#END reset binsha
-						
-						#NOTE: All checkout is performed by the base implementation of update
-						
+						if not dry_run:
+							assert nn not in [r.name for r in rmts]
+							smr = smm.create_remote(nn, sm.url)
+							smr.fetch(progress=progress)
+							
+							# If we have a tracking branch, it should be available
+							# in the new remote as well.
+							if len([r for r in smr.refs if r.remote_head == sm.branch_name]) == 0:
+								raise ValueError("Submodule branch named %r was not available in new submodule remote at %r" % (sm.branch_name, sm.url))
+							# END head is not detached
+							
+							# now delete the changed one
+							rmt_for_deletion = None
+							for remote in rmts:
+								if remote.url == psm.url:
+									rmt_for_deletion = remote
+									break
+								# END if urls match
+							# END for each remote
+							
+							# if we didn't find a matching remote, but have exactly one, 
+							# we can safely use this one
+							if rmt_for_deletion is None:
+								if len(rmts) == 1:
+									rmt_for_deletion = rmts[0]
+								else:
+									# if we have not found any remote with the original url
+									# we may not have a name. This is a special case, 
+									# and its okay to fail here
+									# Alternatively we could just generate a unique name and leave all
+									# existing ones in place
+									raise InvalidGitRepositoryError("Couldn't find original remote-repo at url %r" % psm.url)
+								#END handle one single remote
+							# END handle check we found a remote
+							
+							orig_name = rmt_for_deletion.name
+							smm.delete_remote(rmt_for_deletion)
+							# NOTE: Currently we leave tags from the deleted remotes
+							# as well as separate tracking branches in the possibly totally 
+							# changed repository ( someone could have changed the url to 
+							# another project ). At some point, one might want to clean
+							# it up, but the danger is high to remove stuff the user
+							# has added explicitly
+							
+							# rename the new remote back to what it was
+							smr.rename(orig_name)
+							
+							# early on, we verified that the our current tracking branch
+							# exists in the remote. Now we have to assure that the 
+							# sha we point to is still contained in the new remote
+							# tracking branch.
+							smsha = sm.binsha
+							found = False
+							rref = smr.refs[self.branch_name]
+							for c in rref.commit.traverse():
+								if c.binsha == smsha:
+									found = True
+									break
+								# END traverse all commits in search for sha
+							# END for each commit
+							
+							if not found:
+								# adjust our internal binsha to use the one of the remote
+								# this way, it will be checked out in the next step
+								# This will change the submodule relative to us, so 
+								# the user will be able to commit the change easily
+								print >> sys.stderr, "WARNING: Current sha %s was not contained in the tracking branch at the new remote, setting it the the remote's tracking branch" % sm.hexsha
+								sm.binsha = rref.commit.binsha
+							#END reset binsha
+							
+							#NOTE: All checkout is performed by the base implementation of update
+						#END handle dry_run
+						progress.update(END|URLCHANGE, i, len_csms, prefix+"Done adjusting url of submodule %r" % (sm.name))
 					# END skip remote handling if new url already exists in module
 				# END handle url
 				
+				# HANDLE PATH CHANGES
+				#####################
 				if sm.branch_path != psm.branch_path:
 					# finally, create a new tracking branch which tracks the 
 					# new remote branch
-					smm = sm.module()
-					smmr = smm.remotes
-					try:
-						tbr = git.Head.create(smm, sm.branch_name, logmsg='branch: Created from HEAD')
-					except OSError:
-						# ... or reuse the existing one
-						tbr = git.Head(smm, sm.branch_path)
-					#END assure tracking branch exists
-					
-					tbr.set_tracking_branch(find_first_remote_branch(smmr, sm.branch_name))
-					# figure out whether the previous tracking branch contains
-					# new commits compared to the other one, if not we can 
-					# delete it.
-					try:
-						tbr = find_first_remote_branch(smmr, psm.branch_name)
-						if len(smm.git.cherry(tbr, psm.branch)) == 0:
-							psm.branch.delete(smm, psm.branch)
-						#END delete original tracking branch if there are no changes
-					except InvalidGitRepositoryError:
-						# ignore it if the previous branch couldn't be found in the
-						# current remotes, this just means we can't handle it
-						pass
-					# END exception handling
-					
-					#NOTE: All checkout is done in the base implementation of update
+					progress.update(BEGIN|BRANCHCHANGE, i, len_csms, prefix+"Changing branch of submodule %r from %s to %s" % (sm.name, psm.branch_path, sm.branch_path))
+					if not dry_run:
+						smm = sm.module()
+						smmr = smm.remotes
+						try:
+							tbr = git.Head.create(smm, sm.branch_name, logmsg='branch: Created from HEAD')
+						except OSError:
+							# ... or reuse the existing one
+							tbr = git.Head(smm, sm.branch_path)
+						#END assure tracking branch exists
+						
+						tbr.set_tracking_branch(find_first_remote_branch(smmr, sm.branch_name))
+						# figure out whether the previous tracking branch contains
+						# new commits compared to the other one, if not we can 
+						# delete it.
+						try:
+							tbr = find_first_remote_branch(smmr, psm.branch_name)
+							if len(smm.git.cherry(tbr, psm.branch)) == 0:
+								psm.branch.delete(smm, psm.branch)
+							#END delete original tracking branch if there are no changes
+						except InvalidGitRepositoryError:
+							# ignore it if the previous branch couldn't be found in the
+							# current remotes, this just means we can't handle it
+							pass
+						# END exception handling
+						
+						#NOTE: All checkout is done in the base implementation of update
+					#END handle dry_run
 					
+					progress.update(END|BRANCHCHANGE, i, len_csms, prefix+"Done changing branch of submodule %r" % sm.name)
 				#END handle branch
 			#END handle 
 		# END for each common submodule 
@@ -234,15 +291,20 @@ class RootModule(Submodule):
 		######################################
 		for sm in sms:
 			# update the submodule using the default method
-			sm.update(recursive=False, init=init, to_latest_revision=to_latest_revision)
+			sm.update(recursive=False, init=init, to_latest_revision=to_latest_revision, 
+						progress=progress, dry_run=dry_run)
 			
 			# update recursively depth first - question is which inconsitent 
 			# state will be better in case it fails somewhere. Defective branch
 			# or defective depth. The RootSubmodule type will never process itself, 
 			# which was done in the previous expression
 			if recursive:
-				type(self)(sm.module()).update(recursive=True, force_remove=force_remove, 
-											init=init, to_latest_revision=to_latest_revision)
+				# the module would exist by now if we are not in dry_run mode
+				if sm.module_exists():
+					type(self)(sm.module()).update(	recursive=True, force_remove=force_remove, 
+													init=init, to_latest_revision=to_latest_revision,
+													progress=progress, dry_run=dry_run)
+				#END handle dry_run
 			#END handle recursive
 		# END for each submodule to update
 
diff --git a/remote.py b/remote.py
index 2e596ca1..69a8126b 100644
--- a/remote.py
+++ b/remote.py
@@ -7,14 +7,14 @@
 # Module implementing a remote object allowing easy access to git remotes
 
 from exc import GitCommandError
-from objects import Commit
 from ConfigParser import NoOptionError
 from config import SectionConstraint
 
 from git.util import (
 						LazyMixin,
 						Iterable,
-						IterableList
+						IterableList,
+						RemoteProgress
 						)
 
 from refs import (
@@ -33,123 +33,6 @@ import sys
 
 __all__ = ('RemoteProgress', 'PushInfo', 'FetchInfo', 'Remote')
 
-class RemoteProgress(object):
-	"""
-	Handler providing an interface to parse progress information emitted by git-push
-	and git-fetch and to dispatch callbacks allowing subclasses to react to the progress.
-	"""
-	BEGIN, END, COUNTING, COMPRESSING, WRITING =  [ 1 << x for x in range(5) ]
-	STAGE_MASK = BEGIN|END
-	OP_MASK = COUNTING|COMPRESSING|WRITING
-	
-	__slots__ = ("_cur_line", "_seen_ops")
-	re_op_absolute = re.compile("(remote: )?([\w\s]+):\s+()(\d+)()(.*)")
-	re_op_relative = re.compile("(remote: )?([\w\s]+):\s+(\d+)% \((\d+)/(\d+)\)(.*)")
-	
-	def __init__(self):
-		self._seen_ops = list()
-	
-	def _parse_progress_line(self, line):
-		"""Parse progress information from the given line as retrieved by git-push
-		or git-fetch
-		
-		:return: list(line, ...) list of lines that could not be processed"""
-		# handle
-		# Counting objects: 4, done. 
-		# Compressing objects:	50% (1/2)	\rCompressing objects: 100% (2/2)	\rCompressing objects: 100% (2/2), done.
-		self._cur_line = line
-		sub_lines = line.split('\r')
-		failed_lines = list()
-		for sline in sub_lines:
-			# find esacpe characters and cut them away - regex will not work with 
-			# them as they are non-ascii. As git might expect a tty, it will send them
-			last_valid_index = None
-			for i,c in enumerate(reversed(sline)):
-				if ord(c) < 32:
-					# its a slice index
-					last_valid_index = -i-1 
-				# END character was non-ascii
-			# END for each character in sline
-			if last_valid_index is not None:
-				sline = sline[:last_valid_index]
-			# END cut away invalid part
-			sline = sline.rstrip()
-			
-			cur_count, max_count = None, None
-			match = self.re_op_relative.match(sline)
-			if match is None:
-				match = self.re_op_absolute.match(sline)
-				
-			if not match:
-				self.line_dropped(sline)
-				failed_lines.append(sline)
-				continue
-			# END could not get match
-			
-			op_code = 0
-			remote, op_name, percent, cur_count, max_count, message = match.groups()
-			
-			# get operation id
-			if op_name == "Counting objects":
-				op_code |= self.COUNTING
-			elif op_name == "Compressing objects":
-				op_code |= self.COMPRESSING
-			elif op_name == "Writing objects":
-				op_code |= self.WRITING
-			else:
-				raise ValueError("Operation name %r unknown" % op_name)
-			
-			# figure out stage
-			if op_code not in self._seen_ops:
-				self._seen_ops.append(op_code)
-				op_code |= self.BEGIN
-			# END begin opcode
-			
-			if message is None:
-				message = ''
-			# END message handling
-			
-			message = message.strip()
-			done_token = ', done.'
-			if message.endswith(done_token):
-				op_code |= self.END
-				message = message[:-len(done_token)]
-			# END end message handling
-			
-			self.update(op_code, cur_count, max_count, message)
-		# END for each sub line
-		return failed_lines
-	
-	def line_dropped(self, line):
-		"""Called whenever a line could not be understood and was therefore dropped."""
-		pass
-	
-	def update(self, op_code, cur_count, max_count=None, message=''):
-		"""Called whenever the progress changes
-		
-		:param op_code:
-			Integer allowing to be compared against Operation IDs and stage IDs.
-			
-			Stage IDs are BEGIN and END. BEGIN will only be set once for each Operation 
-			ID as well as END. It may be that BEGIN and END are set at once in case only
-			one progress message was emitted due to the speed of the operation.
-			Between BEGIN and END, none of these flags will be set
-			
-			Operation IDs are all held within the OP_MASK. Only one Operation ID will 
-			be active per call.
-		:param cur_count: Current absolute count of items
-			
-		:param max_count:
-			The maximum count of items we expect. It may be None in case there is 
-			no maximum number of items or if it is (yet) unknown.
-		
-		:param message:
-			In case of the 'WRITING' operation, it contains the amount of bytes
-			transferred. It may possibly be used for other purposes as well.
-		
-		You may read the contents of the current line in self._cur_line"""
-		pass
-		
 		
 class PushInfo(object):
 	"""
diff --git a/test/test_submodule.py b/test/test_submodule.py
index f69c27ea..b8a25e02 100644
--- a/test/test_submodule.py
+++ b/test/test_submodule.py
@@ -4,12 +4,20 @@
 from git.test.lib import *
 from git.exc import *
 from git.objects.submodule.base import Submodule
-from git.objects.submodule.root import RootModule
+from git.objects.submodule.root import RootModule, RootUpdateProgress
 from git.util import to_native_path_linux, join_path_native
 import shutil
 import git
 import os
 
+class TestRootProgress(RootUpdateProgress):
+	"""Just prints messages, for now without checking the correctness of the states"""
+	
+	def update(self, op, index, max_count, message=''):
+		print message
+		
+prog = TestRootProgress()
+
 class TestSubmodule(TestBase):
 
 	k_subm_current = "83a9e4a0dad595188ff3fb35bc3dfc4d931eff6d"
@@ -130,6 +138,10 @@ class TestSubmodule(TestBase):
 			self.failUnlessRaises(OSError, sm.update)
 			os.rmdir(newdir)
 			
+			# dry-run does nothing
+			sm.update(dry_run=True, progress=prog)
+			assert not sm.module_exists()
+			
 			assert sm.update() is sm
 			sm_repopath = sm.path				# cache for later
 			assert sm.module_exists()
@@ -150,6 +162,11 @@ class TestSubmodule(TestBase):
 			
 			# delete the whole directory and re-initialize
 			shutil.rmtree(sm.abspath)
+			assert len(sm.children()) == 0
+			# dry-run does nothing
+			sm.update(dry_run=True, recursive=False, progress=prog)
+			assert len(sm.children()) == 0
+			
 			sm.update(recursive=False)
 			assert len(list(rwrepo.iter_submodules())) == 2
 			assert len(sm.children()) == 1			# its not checked out yet
@@ -162,8 +179,14 @@ class TestSubmodule(TestBase):
 			csm.config_writer().set_value('url', new_csmclone_path)
 			assert csm.url == new_csmclone_path
 			
+			# dry-run does nothing
+			assert not csm.module_exists()
+			sm.update(recursive=True, dry_run=True, progress=prog)
+			assert not csm.module_exists()
+			
 			# update recuesively again
 			sm.update(recursive=True)
+			assert csm.module_exists()
 			
 			# tracking branch once again
 			csm.module().head.ref.tracking_branch() is not None
@@ -175,9 +198,15 @@ class TestSubmodule(TestBase):
 			# reset both heads to the previous version, verify that to_latest_revision works
 			smods = (sm.module(), csm.module())
 			for repo in smods:
-				repo.head.reset('HEAD~1', working_tree=1)
+				repo.head.reset('HEAD~2', working_tree=1)
 			# END for each repo to reset
 			
+			# dry run does nothing 
+			sm.update(recursive=True, dry_run=True, progress=prog)
+			for repo in smods:
+				assert repo.head.commit != repo.head.ref.tracking_branch().commit
+			# END for each repo to check
+			
 			sm.update(recursive=True, to_latest_revision=True)
 			for repo in smods:
 				assert repo.head.commit == repo.head.ref.tracking_branch().commit
@@ -378,6 +407,11 @@ class TestSubmodule(TestBase):
 		
 		# assure we clone from a local source 
 		sm.config_writer().set_value('url', to_native_path_linux(join_path_native(self.rorepo.working_tree_dir, sm.path)))
+		
+		# dry-run does nothing
+		sm.update(recursive=False, dry_run=True, progress=prog)
+		assert not sm.module_exists()
+		
 		sm.update(recursive=False)
 		assert sm.module_exists()
 		sm.config_writer().set_value('path', fp)	# change path to something with prefix AFTER url change
@@ -397,7 +431,7 @@ class TestSubmodule(TestBase):
 		cpathchange = rwrepo.index.commit("changed sm path") # finally we can commit
 		
 		# update puts the module into place
-		rm.update(recursive=False)
+		rm.update(recursive=False, progress=prog)
 		sm.set_parent_commit(cpathchange)
 		assert sm.module_exists()
 		
@@ -415,7 +449,12 @@ class TestSubmodule(TestBase):
 		nsm.remove(configuration=False, module=True)
 		assert not nsm.module_exists() and nsm.exists()
 		
-		rm.update(recursive=False)
+		
+		# dry-run does nothing
+		rm.update(recursive=False, dry_run=True, progress=prog)
+		
+		# otherwise it will work
+		rm.update(recursive=False, progress=prog)
 		assert nsm.module_exists()
 		
 		
@@ -429,6 +468,10 @@ class TestSubmodule(TestBase):
 		csmremoved = rwrepo.index.commit("Removed submodule")
 		
 		# an update will remove the module
+		# not in dry_run
+		rm.update(recursive=False, dry_run=True)
+		assert os.path.isdir(smp)
+		
 		rm.update(recursive=False)
 		assert not os.path.isdir(smp)
 		
@@ -444,7 +487,11 @@ class TestSubmodule(TestBase):
 		nsm.set_parent_commit(csmpathchange)
 		
 		prev_commit = nsm.module().head.commit
-		rm.update(recursive=False)
+		# dry-run does nothing
+		rm.update(recursive=False, dry_run=True, progress=prog)
+		assert nsm.module().remotes.origin.url != nsmurl
+		
+		rm.update(recursive=False, progress=prog)
 		assert nsm.module().remotes.origin.url == nsmurl
 		# head changed, as the remote url and its commit changed
 		assert prev_commit != nsm.module().head.commit
@@ -473,7 +520,12 @@ class TestSubmodule(TestBase):
 		assert nsmmh.ref.tracking_branch() is None					# never set it up until now
 		assert not nsmmh.is_detached
 		
-		rm.update(recursive=False)
+		#dry run does nothing
+		rm.update(recursive=False, dry_run=True, progress=prog)
+		assert nsmmh.ref.tracking_branch() is None
+		
+		# the real thing does
+		rm.update(recursive=False, progress=prog)
 		
 		assert nsmmh.ref.tracking_branch() is not None
 		assert not nsmmh.is_detached
@@ -487,7 +539,8 @@ class TestSubmodule(TestBase):
 		# assure we pull locally only
 		nsmc = nsm.children()[0] 
 		nsmc.config_writer().set_value('url', async_url)
-		rm.update(recursive=True)
+		rm.update(recursive=True, progress=prog, dry_run=True)		# just to run the code
+		rm.update(recursive=True, progress=prog)
 		
-		assert len(nsm.children()) == 1 and nsmc.module_exists() 
+		assert len(nsm.children()) == 1 and nsmc.module_exists()
 		
diff --git a/util.py b/util.py
index 42719233..8c0b6697 100644
--- a/util.py
+++ b/util.py
@@ -22,7 +22,8 @@ from gitdb.util import (
 
 __all__ = ( "stream_copy", "join_path", "to_native_path_windows", "to_native_path_linux", 
 			"join_path_native", "Stats", "IndexFileSHA1Writer", "Iterable", "IterableList", 
-			"BlockingLockFile", "LockFile", 'Actor', 'get_user_id', 'assure_directory_exists')
+			"BlockingLockFile", "LockFile", 'Actor', 'get_user_id', 'assure_directory_exists',
+			'RemoteProgress')
 
 #{ Utility Methods
 
@@ -77,6 +78,7 @@ def join_path_native(a, *p):
 	
 def assure_directory_exists(path, is_file=False):
 	"""Assure that the directory pointed to by path exists.
+	
 	:param is_file: If True, path is assumed to be a file and handled correctly.
 		Otherwise it must be a directory
 	:return: True if the directory was created, False if it already existed"""
@@ -103,6 +105,125 @@ def get_user_id():
 
 #{ Classes
 
+class RemoteProgress(object):
+	"""
+	Handler providing an interface to parse progress information emitted by git-push
+	and git-fetch and to dispatch callbacks allowing subclasses to react to the progress.
+	"""
+	_num_op_codes = 5
+	BEGIN, END, COUNTING, COMPRESSING, WRITING =  [1 << x for x in range(_num_op_codes)]
+	STAGE_MASK = BEGIN|END
+	OP_MASK = ~STAGE_MASK
+	
+	__slots__ = ("_cur_line", "_seen_ops")
+	re_op_absolute = re.compile("(remote: )?([\w\s]+):\s+()(\d+)()(.*)")
+	re_op_relative = re.compile("(remote: )?([\w\s]+):\s+(\d+)% \((\d+)/(\d+)\)(.*)")
+	
+	def __init__(self):
+		self._seen_ops = list()
+	
+	def _parse_progress_line(self, line):
+		"""Parse progress information from the given line as retrieved by git-push
+		or git-fetch
+		
+		:return: list(line, ...) list of lines that could not be processed"""
+		# handle
+		# Counting objects: 4, done. 
+		# Compressing objects:	50% (1/2)	\rCompressing objects: 100% (2/2)	\rCompressing objects: 100% (2/2), done.
+		self._cur_line = line
+		sub_lines = line.split('\r')
+		failed_lines = list()
+		for sline in sub_lines:
+			# find esacpe characters and cut them away - regex will not work with 
+			# them as they are non-ascii. As git might expect a tty, it will send them
+			last_valid_index = None
+			for i,c in enumerate(reversed(sline)):
+				if ord(c) < 32:
+					# its a slice index
+					last_valid_index = -i-1 
+				# END character was non-ascii
+			# END for each character in sline
+			if last_valid_index is not None:
+				sline = sline[:last_valid_index]
+			# END cut away invalid part
+			sline = sline.rstrip()
+			
+			cur_count, max_count = None, None
+			match = self.re_op_relative.match(sline)
+			if match is None:
+				match = self.re_op_absolute.match(sline)
+				
+			if not match:
+				self.line_dropped(sline)
+				failed_lines.append(sline)
+				continue
+			# END could not get match
+			
+			op_code = 0
+			remote, op_name, percent, cur_count, max_count, message = match.groups()
+			
+			# get operation id
+			if op_name == "Counting objects":
+				op_code |= self.COUNTING
+			elif op_name == "Compressing objects":
+				op_code |= self.COMPRESSING
+			elif op_name == "Writing objects":
+				op_code |= self.WRITING
+			else:
+				raise ValueError("Operation name %r unknown" % op_name)
+			
+			# figure out stage
+			if op_code not in self._seen_ops:
+				self._seen_ops.append(op_code)
+				op_code |= self.BEGIN
+			# END begin opcode
+			
+			if message is None:
+				message = ''
+			# END message handling
+			
+			message = message.strip()
+			done_token = ', done.'
+			if message.endswith(done_token):
+				op_code |= self.END
+				message = message[:-len(done_token)]
+			# END end message handling
+			
+			self.update(op_code, cur_count, max_count, message)
+		# END for each sub line
+		return failed_lines
+	
+	def line_dropped(self, line):
+		"""Called whenever a line could not be understood and was therefore dropped."""
+		pass
+	
+	def update(self, op_code, cur_count, max_count=None, message=''):
+		"""Called whenever the progress changes
+		
+		:param op_code:
+			Integer allowing to be compared against Operation IDs and stage IDs.
+			
+			Stage IDs are BEGIN and END. BEGIN will only be set once for each Operation 
+			ID as well as END. It may be that BEGIN and END are set at once in case only
+			one progress message was emitted due to the speed of the operation.
+			Between BEGIN and END, none of these flags will be set
+			
+			Operation IDs are all held within the OP_MASK. Only one Operation ID will 
+			be active per call.
+		:param cur_count: Current absolute count of items
+			
+		:param max_count:
+			The maximum count of items we expect. It may be None in case there is 
+			no maximum number of items or if it is (yet) unknown.
+		
+		:param message:
+			In case of the 'WRITING' operation, it contains the amount of bytes
+			transferred. It may possibly be used for other purposes as well.
+		
+		You may read the contents of the current line in self._cur_line"""
+		pass
+
+
 class Actor(object):
 	"""Actors hold information about a person acting on the repository. They 
 	can be committers and authors or anything with a name and an email as