'git subtree split' can incorrectly skip a merge even when both parents
act on the subtree, provided the merge results in a tree identical to
one of the parents. Fix by copying the merge if at least one parent is
non-identical, and the non-identical parent is not an ancestor of the
identical parent.

Also, add a test case which checks that a descendant remains a
descendent on the subtree in this case.

Signed-off-by: Dave Ware <davidw@realtimegenomics.com>
Reviewed-by: David A. Greene <greened@obbligato.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Test cleanups for the subtree project.

* dg/subtree-test-cleanup:
  contrib/subtree: Handle '--prefix' argument with a slash appended
  contrib/subtree: Make each test self-contained
  contrib/subtree: Add split tests
  contrib/subtree: Add merge tests
  contrib/subtree: Add tests for subtree add
  contrib/subtree: Add test for missing subtree
  contrib/subtree: Clean and refactor test code

Portability fix for a topic already in 'master'.

* dt/http-range:
  http: fix some printf format warnings

* maint:
  http: treat config options sslCAPath and sslCAInfo as paths
  Documentation/diff: give --word-diff-regex=. example
  filter-branch: deal with object name vs. pathname ambiguity in tree-filter
  check-ignore: correct documentation about output
  git-p4: clean up after p4 submit failure
  git-p4: work with a detached head
  git-p4: add option to system() to return subshell status
  git-p4: add failing test for submit from detached head
  remote-http(s): support SOCKS proxies
  t5813: avoid creating urls that break on cygwin
  Escape Git's exec path in contrib/rerere-train.sh script
  allow hooks to ignore their standard input stream
  rebase-i-exec: Allow space in SHELL_PATH
  Documentation: make environment variable formatting more consistent

Just like the working tree is cleaned up when the user cancelled
submission in P4Submit.applyCommit(), clean up the mess if "p4
submit" fails.

* eg/p4-submit-catch-failure:
  git-p4: clean up after p4 submit failure

Documentation clarification for "check-ignore" without "--verbose".

* dk/check-ignore-docs:
  check-ignore: correct documentation about output

Make git-p4 work on a detached head.

* ld/p4-detached-head:
  git-p4: work with a detached head
  git-p4: add option to system() to return subshell status
  git-p4: add failing test for submit from detached head

Fix for a corner case in filter-branch.

* sg/filter-branch-dwim-ambiguity:
  filter-branch: deal with object name vs. pathname ambiguity in tree-filter

* mg/doc-word-diff-example:
  Documentation/diff: give --word-diff-regex=. example

Allow tilde-expansion in some http config variables.

* cb/ssl-config-pathnames:
  http: treat config options sslCAPath and sslCAInfo as paths