IndexFile.commit() now runs pre-commit and post-commit hooks.

However, it does so only on posix. The test-case will run on posix only
as well.
Please note that in theory, even on windows we will attempt to run hooks,
even though I am not sure that this will actually work.

Fixes #81

5 files changed, 87 insertions, 11 deletions

diff --git a/git/cmd.py b/git/cmd.py
index 668d8f4a..2c76710c 100644
--- a/git/cmd.py
+++ b/git/cmd.py
@@ -502,7 +502,7 @@ class Git(LazyMixin):
                      # Prevent cmd prompt popups on windows by using a shell ... .
                      # See https://github.com/gitpython-developers/GitPython/pull/126
                      shell=sys.platform == 'win32',
-                     close_fds=(os.name == 'posix'),  # unsupported on linux
+                     close_fds=(os.name == 'posix'),  # unsupported on windows
                      **subprocess_kwargs
                      )
         if as_process:
diff --git a/git/exc.py b/git/exc.py
index 42191c62..d9b7cbd2 100644
--- a/git/exc.py
+++ b/git/exc.py
@@ -11,17 +11,14 @@ from git.compat import defenc
 
 
 class InvalidGitRepositoryError(Exception):
-
     """ Thrown if the given repository appears to have an invalid format.  """
 
 
 class NoSuchPathError(OSError):
-
     """ Thrown if a path could not be access by the system. """
 
 
 class GitCommandError(Exception):
-
     """ Thrown if execution of the git command fails with non-zero status code. """
 
     def __init__(self, command, status, stderr=None, stdout=None):
@@ -41,7 +38,6 @@ class GitCommandError(Exception):
 
 
 class CheckoutError(Exception):
-
     """Thrown if a file could not be checked out from the index as it contained
     changes.
 
@@ -71,6 +67,20 @@ class CacheError(Exception):
 
 
 class UnmergedEntriesError(CacheError):
-
     """Thrown if an operation cannot proceed as there are still unmerged
     entries in the cache"""
+
+
+class HookExecutionError(Exception):
+    """Thrown if a hook exits with a non-zero exit code. It provides access to the exit code and the string returned
+    via standard output"""
+
+    def __init__(self, command, status, stdout, stderr):
+        self.command = command
+        self.status = status
+        self.stdout = stdout
+        self.stderr = stderr
+
+    def __str__(self):
+        return ("'%s' hook returned with exit code %i\nstdout: '%s'\nstderr: '%s'"
+                % (self.command, self.status, self.stdout, self.stderr))
diff --git a/git/index/base.py b/git/index/base.py
index db0c3cda..7002385c 100644
--- a/git/index/base.py
+++ b/git/index/base.py
@@ -63,7 +63,8 @@ from .fun import (
     aggressive_tree_merge,
     write_tree_from_cache,
     stat_mode_to_index_mode,
-    S_IFGITLINK
+    S_IFGITLINK,
+    run_commit_hook
 )
 
 from gitdb.base import IStream
@@ -893,9 +894,12 @@ class IndexFile(LazyMixin, diff.Diffable, Serializable):
         :note: If you have manually altered the .entries member of this instance,
                don't forget to write() your changes to disk beforehand.
         :return: Commit object representing the new commit"""
+        run_commit_hook('pre-commit', self)
         tree = self.write_tree()
-        return Commit.create_from_tree(self.repo, tree, message, parent_commits,
+        rval = Commit.create_from_tree(self.repo, tree, message, parent_commits,
                                        head, author=author, committer=committer)
+        run_commit_hook('post-commit', self)
+        return rval
 
     @classmethod
     def _flush_stdin_and_wait(cls, proc, ignore_stdout=False):
diff --git a/git/index/fun.py b/git/index/fun.py
index f0dee961..38ad843b 100644
--- a/git/index/fun.py
+++ b/git/index/fun.py
@@ -13,9 +13,14 @@ from stat import (
 S_IFGITLINK = S_IFLNK | S_IFDIR     # a submodule
 
 from io import BytesIO
+import os
+import subprocess
 
 from git.util import IndexFileSHA1Writer
-from git.exc import UnmergedEntriesError
+from git.exc import (
+    UnmergedEntriesError,
+    HookExecutionError
+)
 from git.objects.fun import (
     tree_to_stream,
     traverse_tree_recursive,
@@ -37,10 +42,46 @@ from .util import (
 
 from gitdb.base import IStream
 from gitdb.typ import str_tree_type
-from git.compat import defenc
+from git.compat import (
+    defenc,
+    force_text
+)
 
 __all__ = ('write_cache', 'read_cache', 'write_tree_from_cache', 'entry_key',
-           'stat_mode_to_index_mode', 'S_IFGITLINK')
+           'stat_mode_to_index_mode', 'S_IFGITLINK', 'run_commit_hook', 'hook_path')
+
+
+def hook_path(name, git_dir):
+    """:return: path to the given named hook in the given git repository directory"""
+    return os.path.join(git_dir, 'hooks', name)
+
+
+def run_commit_hook(name, index):
+    """Run the commit hook of the given name. Silently ignores hooks that do not exist.
+    :param name: name of hook, like 'pre-commit'
+    :param index: IndexFile instance
+    :raises HookExecutionError: """
+    hp = hook_path(name, index.repo.git_dir)
+    if not os.access(hp, os.X_OK):
+        return
+
+    env = os.environ.copy()
+    env['GIT_INDEX_FILE'] = index.path
+    env['GIT_EDITOR'] = ':'
+    cmd = subprocess.Popen(hp,
+                           env=env,
+                           stdout=subprocess.PIPE,
+                           stderr=subprocess.PIPE,
+                           close_fds=(os.name == 'posix'))
+    stdout, stderr = cmd.communicate()
+    cmd.stdout.close()
+    cmd.stderr.close()
+
+    if cmd.returncode != 0:
+        stdout = force_text(stdout, defenc)
+        stderr = force_text(stderr, defenc)
+        raise HookExecutionError(hp, cmd.returncode, stdout, stderr)
+    # end handle return code
 
 
 def stat_mode_to_index_mode(mode):
diff --git a/git/test/test_index.py b/git/test/test_index.py
index 021a8cd9..2be776cd 100644
--- a/git/test/test_index.py
+++ b/git/test/test_index.py
@@ -12,6 +12,7 @@ from git.test.lib import (
     with_rw_repo
 )
 from git.util import Actor
+from git.exc import HookExecutionError
 from git import (
     IndexFile,
     BlobFilter,
@@ -40,6 +41,7 @@ from git.index.typ import (
     BaseIndexEntry,
     IndexEntry
 )
+from git.index.fun import hook_path
 
 
 class TestIndex(TestBase):
@@ -665,6 +667,25 @@ class TestIndex(TestBase):
             assert fkey not in index.entries
 
         index.add(files, write=True)
+        if os.name != 'nt':
+            hp = hook_path('pre-commit', index.repo.git_dir)
+            with open(hp, "wt") as fp:
+                fp.write("#!/usr/bin/env sh\necho stdout; echo stderr 1>&2; exit 1")
+            # end
+            os.chmod(hp, 0o544)
+            try:
+                index.commit("This should fail")
+            except HookExecutionError as err:
+                assert err.status == 1
+                assert err.command == hp
+                assert err.stdout == 'stdout\n'
+                assert err.stderr == 'stderr\n'
+                assert str(err)
+            else:
+                raise AssertionError("Should have cought a HookExecutionError")
+            # end exception handling
+            os.remove(hp)
+        # end hook testing
         nc = index.commit("2 files committed", head=False)
 
         for fkey in keys: