[PATCH] filter-branch: add git_commit_non_empty_tree and --prune-empty.

From

Pierre Habouzit <madcoder@debian.org>

Date

Oct 31, 2008, 09:26 UTC

Message-ID

<1225445204-28000-1-git-send-email-madcoder@debian.org>

In-Reply-To

<20081030132623.GC24098@artemis.corp>

Signed-off-by: Pierre Habouzit <madcoder@debian.org>
---

  Okay, this one is meant for inclusion, and has a test case.

  Note that this prune-empty option is not 100% perfect, for example, it won't
  prune an empty base (an empty commit whose parent is 0000000) since it has
  no parent, or won't reduce histories this way:

     t0---t1---t1            t0---t1
              /     ---->        /
             t2                t2

  But I don't think it's especially bad since such trees happen when one does
  'git merge -s ours' all the time, and I don't think git-filter-branch should
  erase those (I mean some people may want to, but then they can figure out
  how to do that by themselves, I don't think it's a common wish).

  The goal of --prune-empty is rather meant to be used e.g. when you remove a
  file from your history, and want to get rid of commits that only touched it,
  or that you want to extract the history of a given subdirectory only and
  remove commits that didn't touch that directory.

 Documentation/git-filter-branch.txt |   14 ++++++++++++++
 git-filter-branch.sh                |   29 ++++++++++++++++++++++++++++-
 t/t7003-filter-branch.sh            |    8 ++++++++
 3 files changed, 50 insertions(+), 1 deletions(-)

diff --git a/Documentation/git-filter-branch.txt b/Documentation/git-filter-branch.txt
index fed6de6..451950b 100644
--- a/Documentation/git-filter-branch.txt
+++ b/Documentation/git-filter-branch.txt
@@ -122,6 +122,10 @@ You can use the 'map' convenience function in this filter, and other
 convenience functions, too.  For example, calling 'skip_commit "$@"'
 will leave out the current commit (but not its changes! If you want
 that, use 'git-rebase' instead).
++
+You can also use the 'git_commit_non_empty_tree "$@"' instead of
+'git commit-tree "$@"' if you don't wish to keep commits with a single parent
+and that makes no change to the tree.
 
 --tag-name-filter <command>::
 	This is the filter for rewriting tag names. When passed,
@@ -151,6 +155,16 @@ to other tags will be rewritten to point to the underlying commit.
 	The result will contain that directory (and only that) as its
 	project root.
 
+--prune-empty::
+	Some kind of filters will generate empty commits, that left the tree
+	untouched.  This switch allow git-filter-branch to ignore such
+	commits.  Though, this switch only applies for commits that have one
+	and only one parent, it will hence keep merges points. Also, this
+	option is not compatible with the use of '--commit-filter'. Though you
+	just need to use the function 'git_commit_non_empty_tree "$@"' instead
+	of the 'git commit-tree "$@"' idiom in your commit filter to make that
+	happen.
+
 --original <namespace>::
 	Use this option to set the namespace where the original commits
 	will be stored. The default value is 'refs/original'.
diff --git a/git-filter-branch.sh b/git-filter-branch.sh
index 81392ad..4827934 100755
--- a/git-filter-branch.sh
+++ b/git-filter-branch.sh
@@ -40,6 +40,16 @@ skip_commit()
 	done;
 }
 
+# if you run 'git_commit_non_empty_tree "$@"' in a commit filter,
+# it will skip commits that leave the tree untouched, commit the other.
+git_commit_non_empty_tree()
+{
+	if test $# = 3 && test "$1" = $(git rev-parse "$3^{tree}"); then
+		map "$3"
+	else
+		git commit-tree "$@"
+	fi
+}
 # override die(): this version puts in an extra line break, so that
 # the progress is still visible
 
@@ -109,11 +119,12 @@ filter_tree=
 filter_index=
 filter_parent=
 filter_msg=cat
-filter_commit='git commit-tree "$@"'
+filter_commit=
 filter_tag_name=
 filter_subdir=
 orig_namespace=refs/original/
 force=
+prune_empty=
 while :
 do
 	case "$1" in
@@ -126,6 +137,11 @@ do
 		force=t
 		continue
 		;;
+	--prune-empty)
+		shift
+		prune_empty=t
+		continue
+		;;
 	-*)
 		;;
 	*)
@@ -176,6 +192,17 @@ do
 	esac
 done
 
+case "$prune_empty,$filter_commit" in
+',')
+	filter_commit='git commit-tree "$@"';;
+'t,')
+	filter_commit="$functions;"' git_commit_non_empty_tree "$@"';;
+','*)
+	;;
+*)
+	die "Cannot set --prune-empty and --filter-commit at the same time"
+esac
+
 case "$force" in
 t)
 	rm -rf "$tempdir"
diff --git a/t/t7003-filter-branch.sh b/t/t7003-filter-branch.sh
index b0a9d7d..352b56b 100755
--- a/t/t7003-filter-branch.sh
+++ b/t/t7003-filter-branch.sh
@@ -262,4 +262,12 @@ test_expect_success 'Tag name filtering allows slashes in tag names' '
 	test_cmp expect actual
 '
 
+test_expect_success 'Prune empty commits' '
+	make_commit to_remove &&
+	(git rev-list HEAD | grep -v $(git rev-parse HEAD)) > expect &&
+	git filter-branch -f --index-filter "git update-index --remove to_remove" --prune-empty HEAD &&
+	git rev-list HEAD > actual &&
+	test_cmp expect actual
+'
+
 test_done

-- 
1.6.0.3.757.gf86e6.dirty