[PATCH 1/3] range-diff: refactor check for commit range

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

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

Currently, when called with exactly two arguments, we test for a literal
`..` in each of the two.

However, `<commit>^!` is a perfectly valid commit range, equivalent to
`<commit>^..<commit>` according to the `SPECIFYING RANGES` section of
gitrevisions[7].

In preparation for allowing more sophisticated ways to specify commit
ranges, let's refactor the conditional into its own function.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 builtin/range-diff.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/builtin/range-diff.c b/builtin/range-diff.c
index 24c4162f744..551d3e689cb 100644
--- a/builtin/range-diff.c
+++ b/builtin/range-diff.c
@@ -11,6 +11,11 @@ N_("git range-diff [<options>] <base> <old-tip> <new-tip>"),
 NULL
 };
 
+static int is_range(const char *range)
+{
+	return !!strstr(range, "..");
+}
+
 int cmd_range_diff(int argc, const char **argv, const char *prefix)
 {
 	int creation_factor = RANGE_DIFF_CREATION_FACTOR_DEFAULT;
@@ -46,12 +51,12 @@ int cmd_range_diff(int argc, const char **argv, const char *prefix)
 		diffopt.use_color = 1;
 
 	if (argc == 2) {
-		if (!strstr(argv[0], ".."))
-			die(_("no .. in range: '%s'"), argv[0]);
+		if (!is_range(argv[0]))
+			die(_("not a commit range: '%s'"), argv[0]);
 		strbuf_addstr(&range1, argv[0]);
 
-		if (!strstr(argv[1], ".."))
-			die(_("no .. in range: '%s'"), argv[1]);
+		if (!is_range(argv[1]))
+			die(_("not a commit range: '%s'"), argv[1]);
 		strbuf_addstr(&range2, argv[1]);
 	} else if (argc == 3) {
 		strbuf_addf(&range1, "%s..%s", argv[0], argv[1]);
-- 
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