filter-branch: retire --remap-to-ancestor

We can be clever and know by ourselves when we need the behavior
implied by "--remap-to-ancestor". No need to encumber users by having
them exposed to it as a tunable. (Option kept for backward compatibility,
but it's now a no-op.)

Signed-off-by: Csaba Henk <csaba@gluster.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-filter-branch.txt

@@ -159,18 +159,7 @@ 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.  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.
+	project root. Implies <<Remap_to_ancestor>>.
 
 --prune-empty::
 	Some kind of filters will generate empty commits, that left the tree
@@ -204,7 +193,18 @@ the nearest ancestor that was not excluded.
 	Arguments for 'git rev-list'.  All positive refs included by
 	these options are rewritten.  You may also specify options
 	such as '--all', but you must use '--' to separate them from
-	the 'git filter-branch' options.
+	the 'git filter-branch' options. Implies <<Remap_to_ancestor>>.
+
+
+[[Remap_to_ancestor]]
+Remap to ancestor
+~~~~~~~~~~~~~~~~~
+
+By using linkgit:rev-list[1] arguments, e.g., path limiters, you can limit the
+set of revisions which get rewritten. However, positive refs on the command
+line are distinguished: we don't let them be excluded by such limiters. For
+this purpose, they are instead rewritten to point at the nearest ancestor that
+was not excluded.
 
 
 Examples

git-filter-branch.sh

@@ -139,6 +139,7 @@ do
 		continue
 		;;
 	--remap-to-ancestor)
+		# deprecated ($remap_to_ancestor is set now automatically)
 		shift
 		remap_to_ancestor=t
 		continue
@@ -265,7 +266,14 @@ 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=
+if test -z "$nonrevs"
+then
+	dashdash=--
+else
+	dashdash=
+	remap_to_ancestor=t
+fi
+
 rev_args=$(git rev-parse --revs-only "$@")
 
 case "$filter_subdir" in

t/t7003-filter-branch.sh

@@ -307,6 +307,24 @@ test_expect_success '--remap-to-ancestor with filename filters' '
 	test $orig_invariant = $(git rev-parse invariant)
 '
 
+test_expect_success 'automatic remapping to ancestor with filename filters' '
+	git checkout master &&
+	git reset --hard A &&
+	test_commit add-foo2 foo 1 &&
+	git branch moved-foo2 &&
+	test_commit add-bar2 bar a &&
+	git branch invariant2 &&
+	orig_invariant=$(git rev-parse invariant2) &&
+	git branch moved-bar2 &&
+	test_commit change-foo2 foo 2 &&
+	git filter-branch -f \
+		moved-foo2 moved-bar2 A..master \
+		-- -- foo &&
+	test $(git rev-parse moved-foo2) = $(git rev-parse moved-bar2) &&
+	test $(git rev-parse moved-foo2) = $(git rev-parse master^) &&
+	test $orig_invariant = $(git rev-parse invariant2)
+'
+
 test_expect_success 'setup submodule' '
 	rm -fr ?* .git &&
 	git init &&