Merge branch 'tr/filter-branch'

* tr/filter-branch:
  filter-branch: nearest-ancestor rewriting outside subdir filter
  filter-branch: stop special-casing $filter_subdir argument

Documentation/git-filter-branch.txt

@@ -159,7 +159,18 @@ to other tags will be rewritten to point to the underlying commit.
 --subdirectory-filter <directory>::
 	Only look at the history which touches the given subdirectory.
 	The result will contain that directory (and only that) as its
-	project root.
+	project root.  Implies --remap-to-ancestor.
+
+--remap-to-ancestor::
+	Rewrite refs to the nearest rewritten ancestor instead of
+	ignoring them.
++
+Normally, positive refs on the command line are only changed if the
+commit they point to was rewritten.  However, you can limit the extent
+of this rewriting by using linkgit:rev-list[1] arguments, e.g., path
+limiters.  Refs pointing to such excluded commits would then normally
+be ignored.  With this option, they are instead rewritten to point at
+the nearest ancestor that was not excluded.
 
 --prune-empty::
 	Some kind of filters will generate empty commits, that left the tree

git-filter-branch.sh

@@ -125,6 +125,7 @@ filter_subdir=
 orig_namespace=refs/original/
 force=
 prune_empty=
+remap_to_ancestor=
 while :
 do
 	case "$1" in
@@ -137,6 +138,11 @@ do
 		force=t
 		continue
 		;;
+	--remap-to-ancestor)
+		shift
+		remap_to_ancestor=t
+		continue
+		;;
 	--prune-empty)
 		shift
 		prune_empty=t
@@ -182,6 +188,7 @@ do
 		;;
 	--subdirectory-filter)
 		filter_subdir="$OPTARG"
+		remap_to_ancestor=t
 		;;
 	--original)
 		orig_namespace=$(expr "$OPTARG/" : '\(.*[^/]\)/*$')/
@@ -257,15 +264,24 @@ git read-tree || die "Could not seed the index"
 # map old->new commit ids for rewriting parents
 mkdir ../map || die "Could not create map/ directory"
 
+# we need "--" only if there are no path arguments in $@
+nonrevs=$(git rev-parse --no-revs "$@") || exit
+test -z "$nonrevs" && dashdash=-- || dashdash=
+rev_args=$(git rev-parse --revs-only "$@")
+
 case "$filter_subdir" in
 "")
-	git rev-list --reverse --topo-order --default HEAD \
-		--parents --simplify-merges "$@"
+	eval set -- "$(git rev-parse --sq --no-revs "$@")"
 	;;
 *)
-	git rev-list --reverse --topo-order --default HEAD \
-		--parents --simplify-merges "$@" -- "$filter_subdir"
-esac > ../revs || die "Could not get the commits"
+	eval set -- "$(git rev-parse --sq --no-revs "$@" $dashdash \
+		"$filter_subdir")"
+	;;
+esac
+
+git rev-list --reverse --topo-order --default HEAD \
+	--parents --simplify-merges $rev_args "$@" > ../revs ||
+	die "Could not get the commits"
 commits=$(wc -l <../revs | tr -d " ")
 
 test $commits -eq 0 && die "Found nothing to rewrite"
@@ -345,19 +361,19 @@ while read commit parents; do
 			die "could not write rewritten commit"
 done <../revs
 
-# In case of a subdirectory filter, it is possible that a specified head
-# is not in the set of rewritten commits, because it was pruned by the
-# revision walker.  Fix it by mapping these heads to the unique nearest
-# ancestor that survived the pruning.
+# If we are filtering for paths, as in the case of a subdirectory
+# filter, it is possible that a specified head is not in the set of
+# rewritten commits, because it was pruned by the revision walker.
+# Ancestor remapping fixes this by mapping these heads to the unique
+# nearest ancestor that survived the pruning.
 
-if test "$filter_subdir"
+if test "$remap_to_ancestor" = t
 then
 	while read ref
 	do
 		sha1=$(git rev-parse "$ref"^0)
 		test -f "$workdir"/../map/$sha1 && continue
-		ancestor=$(git rev-list --simplify-merges -1 \
-				$ref -- "$filter_subdir")
+		ancestor=$(git rev-list --simplify-merges -1 "$ref" "$@")
 		test "$ancestor" && echo $(map $ancestor) >> "$workdir"/../map/$sha1
 	done < "$tempdir"/heads
 fi

t/t7003-filter-branch.sh

@@ -288,4 +288,22 @@ test_expect_success 'Prune empty commits' '
 	test_cmp expect actual
 '
 
+test_expect_success '--remap-to-ancestor with filename filters' '
+	git checkout master &&
+	git reset --hard A &&
+	test_commit add-foo foo 1 &&
+	git branch moved-foo &&
+	test_commit add-bar bar a &&
+	git branch invariant &&
+	orig_invariant=$(git rev-parse invariant) &&
+	git branch moved-bar &&
+	test_commit change-foo foo 2 &&
+	git filter-branch -f --remap-to-ancestor \
+		moved-foo moved-bar A..master \
+		-- -- foo &&
+	test $(git rev-parse moved-foo) = $(git rev-parse moved-bar) &&
+	test $(git rev-parse moved-foo) = $(git rev-parse master^) &&
+	test $orig_invariant = $(git rev-parse invariant)
+'
+
 test_done