[PATCH v2 1/3] range-diff: reorder argument handling

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

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

In d9c66f0b5bf (range-diff: first rudimentary implementation,
2018-08-13), we introduced the argument handling of the `range-diff`
command, special-casing three different stanzas based on the argument
count.

The somewhat unorthodox order (first handling the case of 2 arguments,
then 3, then 1) was chosen for clarity: the natural argument number is 2
because that is how many revision ranges are used internally. The code
to handle three arguments is relatively trivial, so it was added next.
And finally, the code to ungarble a single symmetric range into two
separate ones was added, because it was the most complicated (the most
inelegant part being about interpreting empty sides of the symmetric
range as `HEAD`).

In preparation for allowing pathspecs in `git range-diff` invocations,
where we no longer have the luxury of using the number of arguments to
disambiguate between these three different ways to specify the commit
ranges, we need to order these cases by argument count, in descending
order.

This patch is best viewed with `--color-moved`.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 builtin/range-diff.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/builtin/range-diff.c b/builtin/range-diff.c
index 50318849d65..f8d3869d357 100644
--- a/builtin/range-diff.c
+++ b/builtin/range-diff.c
@@ -55,7 +55,10 @@ int cmd_range_diff(int argc, const char **argv, const char *prefix)
 	if (!simple_color)
 		diffopt.use_color = 1;
 
-	if (argc == 2) {
+	if (argc == 3) {
+		strbuf_addf(&range1, "%s..%s", argv[0], argv[1]);
+		strbuf_addf(&range2, "%s..%s", argv[0], argv[2]);
+	} else if (argc == 2) {
 		if (!is_range_diff_range(argv[0]))
 			die(_("not a commit range: '%s'"), argv[0]);
 		strbuf_addstr(&range1, argv[0]);
@@ -63,9 +66,6 @@ int cmd_range_diff(int argc, const char **argv, const char *prefix)
 		if (!is_range_diff_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]);
-		strbuf_addf(&range2, "%s..%s", argv[0], argv[2]);
 	} else if (argc == 1) {
 		const char *b = strstr(argv[0], "..."), *a = argv[0];
 		int a_len;
-- 
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