[PATCH] Add --unannotate option to git-subtree

From: James Nylen <jnylen@gmail.com>
Date: Oct 9, 2012, 20:26 UTC
Message-ID: <CABVa4NinSighUn7GKbzMx9qZj3Ao2dCtEZxUqCPwO9TocZ8Kkg@mail.gmail.com>

This new option does the reverse of --annotate, which is more useful when contributing back to a library which is also included in the repository for a larger project, and perhaps in other situations as well.

Rather than adding a marker to each commit when splitting out the commits back to the subproject, --unannotate removes the specified string (or bash glob pattern) from the beginning of the first line of the commit message. This enables the following workflow:

 - Commit to a library included in a large project, with message:
     Library: Make some amazing change

 - Use `git-subtree split` to send this change to the library maintainer

 - Pass ` --unannotate='Library: ' ` or ` --unannotate='*: ' `

 - This will turn the commit message for the library project into:
     Make some amazing change

This helps to keep the commit messages meaningful in both the large project and the library project.

Signed-off-by: James Nylen <jnylen@gmail.com>
---
Let me know if gmail has munged this patch.  You can also get at it
like this:

$ git remote add nylen git://github.com/nylen/git.git
$ git fetch nylen
$ git show nylen/subtree-unannotate
---
 contrib/subtree/git-subtree.sh  | 11 +++++++++--
 contrib/subtree/git-subtree.txt | 15 +++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
index 920c664..8d1ed05 100755
--- a/contrib/subtree/git-subtree.sh
+++ b/contrib/subtree/git-subtree.sh
@@ -21,6 +21,7 @@ P,prefix=     the name of the subdir to split out
 m,message=    use the given message as the commit message for the merge commit
  options for 'split'
 annotate=     add a prefix to commit message of new commits
+unannotate=   remove a prefix from new commit messages (supports bash globbing)
 b,branch=     create a new branch from the split subtree
 ignore-joins  ignore prior --rejoin commits
 onto=         try connecting new tree to an existing one
@@ -43,6 +44,7 @@ onto=
 rejoin=
 ignore_joins=
 annotate=
+unannotate=
 squash=
 message=

@@ -80,6 +82,8 @@ while [ $# -gt 0 ]; do
 		-d) debug=1 ;;
 		--annotate) annotate="$1"; shift ;;
 		--no-annotate) annotate= ;;
+		--unannotate) unannotate="$1"; shift ;;
+		--no-unannotate) unannotate= ;;
 		-b) branch="$1"; shift ;;
 		-P) prefix="$1"; shift ;;
 		-m) message="$1"; shift ;;
@@ -310,8 +314,11 @@ copy_commit()
 			GIT_COMMITTER_NAME \
 			GIT_COMMITTER_EMAIL \
 			GIT_COMMITTER_DATE
-		(echo -n "$annotate"; cat ) |
-		git commit-tree "$2" $3  # reads the rest of stdin
+		(
+			read FIRST_LINE
+			echo "$annotate${FIRST_LINE#$unannotate}"
+			cat  # reads the rest of stdin
+		) | git commit-tree "$2" $3
 	) || die "Can't copy commit $1"
 }

diff --git a/contrib/subtree/git-subtree.txt b/contrib/subtree/git-subtree.txt
index 0c44fda..ae420aa 100644
--- a/contrib/subtree/git-subtree.txt
+++ b/contrib/subtree/git-subtree.txt
@@ -198,6 +198,21 @@ OPTIONS FOR split
 	git subtree tries to make it work anyway, particularly
 	if you use --rejoin, but it may not always be effective.

+--unannotate=<annotation>::
+	This option is only valid for the split command.
+
+	When generating synthetic history, try to remove the prefix
+	<annotation> from each commit message (using bash's "strip
+	shortest match from beginning" command, which supports
+	globbing).  This makes sense if you format library commits
+	like "library: Change something or other" when you're working
+	in your project's repository, but you want to remove this
+	prefix when pushing back to the library's upstream repository.
+	(In this case --unannotate='*: ' would work well.)
+	
+	Like --annotate,  you need to use the same <annotation>
+	whenever you split, or you may run into problems.
+
 -b <branch>::
 --branch=<branch>::
 	This option is only valid for the split command.

-- 
1.7.11.3