[PATCH v4 2/3] range-diff/format-patch: handle commit ranges other than A..B

["Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>]

From: Johannes Schindelin <johannes.schindelin@gmx.de>

In the `SPECIFYING RANGES` section of gitrevisions[7], two ways are
described to specify commit ranges that `range-diff` does not yet
accept: "<commit>^!" and "<commit>^-<n>".

Let's accept them, by parsing them via the revision machinery and
looking for at least one interesting and one uninteresting revision in
the resulting `pending` array.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 range-diff.c          | 19 ++++++++++++++++++-
 t/t3206-range-diff.sh |  8 ++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/range-diff.c b/range-diff.c
index 9b93e08e8407..07e212d5bb8c 100644
--- a/range-diff.c
+++ b/range-diff.c
@@ -11,6 +11,7 @@
 #include "pretty.h"
 #include "userdiff.h"
 #include "apply.h"
+#include "revision.h"
 
 struct patch_util {
 	/* For the search for an exact match */
@@ -567,5 +568,21 @@ int show_range_diff(const char *range1, const char *range2,
 
 int is_range_diff_range(const char *arg)
 {
-	return !!strstr(arg, "..");
+	char *copy = xstrdup(arg); /* setup_revisions() modifies it */
+	const char *argv[] = { "", copy, "--", NULL };
+	int i, positive = 0, negative = 0;
+	struct rev_info revs;
+
+	init_revisions(&revs, NULL);
+	if (setup_revisions(3, argv, &revs, 0) == 1) {
+		for (i = 0; i < revs.pending.nr; i++)
+			if (revs.pending.objects[i].item->flags & UNINTERESTING)
+				negative++;
+			else
+				positive++;
+	}
+
+	free(copy);
+	object_array_clear(&revs.pending);
+	return negative > 0 && positive > 0;
 }
diff --git a/t/t3206-range-diff.sh b/t/t3206-range-diff.sh
index 6eb344be0312..e217cecac9ed 100755
--- a/t/t3206-range-diff.sh
+++ b/t/t3206-range-diff.sh
@@ -150,6 +150,14 @@ test_expect_success 'simple A B C (unmodified)' '
 	test_cmp expect actual
 '
 
+test_expect_success 'A^! and A^-<n> (unmodified)' '
+	git range-diff --no-color topic^! unmodified^-1 >actual &&
+	cat >expect <<-EOF &&
+	1:  $(test_oid t4) = 1:  $(test_oid u4) s/12/B/
+	EOF
+	test_cmp expect actual
+'
+
 test_expect_success 'trivial reordering' '
 	git range-diff --no-color master topic reordered >actual &&
 	cat >expect <<-EOF &&
-- 
gitgitgadget