[PATCH v3 5/5] add -p: ignore dirty submodules

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

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

Thanks to alwyas running `diff-index` and `diff-files` with the
`--numstat` option (the latter with `--ignore-submodules=dirty`) before
even generating any real diff to parse, the Perl version of `git add -p`
simply ignored dirty submodules and does not even offer them up for
staging.

However, the built-in variant did not use that flag because it tries to
run only one `diff` command, skipping the unneeded
`diff-index`/`diff-files` invocation of the Perl variant and therefore
only faithfully recapitulates what the Perl code does once it _does_
generate and parse the real diff.

This causes a problem when running the built-in `add -p` with
`diff-so-fancy` because that diff colorizer always inserts an empty line
before the diff header to ensure that it produces 4 lines as expected by
`git add -p` (the equivalent of the non-colorized `diff`, `index`, `---`
and `+++` lines). But `git diff-files` does not produce any `index` line
for dirty submodules.

The underlying problem is not even the discrepancy in lines, but that
`git add -p` presents diffs for dirty submodules: there is nothing that
_can_ be staged for those.

Let's fix that bug, and teach the built-in `add -p` to ignore dirty
submodules, too. This _incidentally_ also fixes the `diff-so-fancy`
problem ;-)

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 add-patch.c                |  3 ++-
 t/t3701-add-interactive.sh | 12 ++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/add-patch.c b/add-patch.c
index 0217cdd7c4a..ee6a3d3b712 100644
--- a/add-patch.c
+++ b/add-patch.c
@@ -426,7 +426,8 @@ static int parse_diff(struct add_p_state *s, const struct pathspec *ps)
 	}
 	color_arg_index = args.nr;
 	/* Use `--no-color` explicitly, just in case `diff.color = always`. */
-	strvec_pushl(&args, "--no-color", "-p", "--", NULL);
+	strvec_pushl(&args, "--no-color", "--ignore-submodules=dirty", "-p",
+		     "--", NULL);
 	for (i = 0; i < ps->nr; i++)
 		strvec_push(&args, ps->items[i].original);
 
diff --git a/t/t3701-add-interactive.sh b/t/t3701-add-interactive.sh
index 39e68b6d066..a4f45fc48a0 100755
--- a/t/t3701-add-interactive.sh
+++ b/t/t3701-add-interactive.sh
@@ -965,6 +965,18 @@ test_expect_success 'status ignores dirty submodules (except HEAD)' '
 	! grep dirty-otherwise output
 '
 
+test_expect_success 'handle submodules' '
+	echo 123 >>for-submodules/dirty-otherwise/initial.t &&
+
+	force_color git -C for-submodules add -p dirty-otherwise >output 2>&1 &&
+	grep "No changes" output &&
+
+	force_color git -C for-submodules add -p dirty-head >output 2>&1 <y &&
+	git -C for-submodules ls-files --stage dirty-head >actual &&
+	rev="$(git -C for-submodules/dirty-head rev-parse HEAD)" &&
+	grep "$rev" actual
+'
+
 test_expect_success 'set up pathological context' '
 	git reset --hard &&
 	test_write_lines a a a a a a a a a a a >a &&
-- 
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