[PATCH] xdiff: trim common tail with -U0 after diff

[Daniel Hahler <git@thequod.de>]

When -U0 is used, trim_common_tail should be called after `xdl_diff`, so
that `--indent-heuristic` (and other diff processing) works as expected.

It also removes the check for `!(xecfg->flags & XDL_EMIT_FUNCCONTEXT)`
added in e0876bca4, which does not appear to be necessary anymore after
moving the trimming down.

This only adds a test to t4061-diff-indent.sh, but should also have one for
normal (i.e. non-experimental) diff mode probably?!

Ref: https://github.com/tomtom/quickfixsigns_vim/issues/74#issue-237900460
---
 t/t4061-diff-indent.sh | 15 +++++++++++++++
 xdiff-interface.c      |  7 ++++---
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/t/t4061-diff-indent.sh b/t/t4061-diff-indent.sh
index 2affd7a10..df3151393 100755
--- a/t/t4061-diff-indent.sh
+++ b/t/t4061-diff-indent.sh
@@ -116,6 +116,16 @@ test_expect_success 'prepare' '
 	 4
 	EOF
 
+	cat <<-\EOF >spaces-compacted-U0-expect &&
+	diff --git a/spaces.txt b/spaces.txt
+	--- a/spaces.txt
+	+++ b/spaces.txt
+	@@ -4,0 +5,3 @@ a
+	+b
+	+a
+	+
+	EOF
+
 	tr "_" " " <<-\EOF >functions-expect &&
 	diff --git a/functions.c b/functions.c
 	--- a/functions.c
@@ -184,6 +194,11 @@ test_expect_success 'diff: --indent-heuristic with --histogram' '
 	compare_diff spaces-compacted-expect out-compacted4
 '
 
+test_expect_success 'diff: --indent-heuristic with -U0' '
+	git diff -U0 --indent-heuristic old new -- spaces.txt >out-compacted5 &&
+	compare_diff spaces-compacted-U0-expect out-compacted5
+'
+
 test_expect_success 'diff: ugly functions' '
 	git diff --no-indent-heuristic old new -- functions.c >out &&
 	compare_diff functions-expect out
diff --git a/xdiff-interface.c b/xdiff-interface.c
index d3f78ca2a..a7e0e3583 100644
--- a/xdiff-interface.c
+++ b/xdiff-interface.c
@@ -125,16 +125,17 @@ static void trim_common_tail(mmfile_t *a, mmfile_t *b)
 
 int xdi_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, xdemitconf_t const *xecfg, xdemitcb_t *xecb)
 {
+	int ret;
 	mmfile_t a = *mf1;
 	mmfile_t b = *mf2;
 
 	if (mf1->size > MAX_XDIFF_SIZE || mf2->size > MAX_XDIFF_SIZE)
 		return -1;
 
-	if (!xecfg->ctxlen && !(xecfg->flags & XDL_EMIT_FUNCCONTEXT))
+	ret = xdl_diff(&a, &b, xpp, xecfg, xecb);
+	if (ret && !xecfg->ctxlen)
 		trim_common_tail(&a, &b);
-
-	return xdl_diff(&a, &b, xpp, xecfg, xecb);
+	return ret;
 }
 
 int xdi_diff_outf(mmfile_t *mf1, mmfile_t *mf2,
-- 
2.13.1