[PATCH 0/2] diff --no-index pager cleanups

[PATCH 0/2] diff --no-index pager cleanups

[Jeff King]

While testing Tim's broken case, I noticed a few annoyances with the
pager handling. These patches should clear them up.

  [1/2]: fix pager.diff with diff --no-index
  [2/2]: do not run pager with diff --no-index --quiet

-Peff

[PATCH 1/2] fix pager.diff with diff --no-index

[Jeff King]

git-diff does not rely on the git wrapper to setup its
pager; instead, it sets it up on its own after seeing
whether --quiet or --exit-code has been specified.  After
diff_no_index was split off from cmd_diff, commit b3fde6c
(git diff --no-index: default to page like other diff
frontends, 2008-05-26) duplicated the one-liner from
cmd_diff to turn on the pager.

Later, commit 8f0359f (Allow pager of diff command be
enabled/disabled, 2008-07-21) taught the the version in
cmd_diff to respect the pager.diff config, but the version
in diff_no_index was left behind. This meant that

  git -c pager.diff=0 diff a b

would not use a pager, but

  git -c pager.diff=0 diff --no-index a b

would.  Let's fix it by factoring out a common function.

While we're there, let's update the antiquated comment,
which claims that the pager interferes with propagating the
exit code; this has not been the case since ea27a18 (spawn
pager via run_command interface, 2008-07-22).

Signed-off-by: Jeff King <peff@peff.net>
---
 builtin.h       |  2 ++
 builtin/diff.c  | 24 +++++++++++++++++-------
 diff-no-index.c |  7 +------
 3 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/builtin.h b/builtin.h
index 338f540..e426de3 100644
--- a/builtin.h
+++ b/builtin.h
@@ -41,6 +41,8 @@ int copy_note_for_rewrite(struct notes_rewrite_cfg *c,
 void finish_copy_notes_for_rewrite(struct notes_rewrite_cfg *c);
 
 extern int check_pager_config(const char *cmd);
+struct diff_options;
+extern void setup_diff_pager(struct diff_options *);
 
 extern int textconv_object(const char *path, unsigned mode, const unsigned char *sha1, char **buf, unsigned long *buf_size);
 
diff --git a/builtin/diff.c b/builtin/diff.c
index 9069dc4..da8f6aa 100644
--- a/builtin/diff.c
+++ b/builtin/diff.c
@@ -304,13 +304,7 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 
 	DIFF_OPT_SET(&rev.diffopt, RECURSIVE);
 
-	/*
-	 * If the user asked for our exit code then don't start a
-	 * pager or we would end up reporting its exit code instead.
-	 */
-	if (!DIFF_OPT_TST(&rev.diffopt, EXIT_WITH_STATUS) &&
-	    check_pager_config("diff") != 0)
-		setup_pager();
+	setup_diff_pager(&rev.diffopt);
 
 	/*
 	 * Do we have --cached and not have a pending object, then
@@ -421,3 +415,19 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 		refresh_index_quietly();
 	return result;
 }
+
+void setup_diff_pager(struct diff_options *opt)
+{
+	/*
+	 * If the user asked for our exit code, then either they want --quiet
+	 * or --exit-code. We should definitely not bother with a pager in the
+	 * former case, as we will generate no output. Since we still properly
+	 * report our exit code even when a pager is run, we _could_ run a
+	 * pager with --exit-code. But since we have not done so historically,
+	 * and because it is easy to find people oneline advising "git diff
+	 * --exit-code" in hooks and other scripts, we do not do so.
+	 */
+	if (!DIFF_OPT_TST(opt, EXIT_WITH_STATUS) &&
+	    check_pager_config("diff") != 0)
+		setup_pager();
+}
diff --git a/diff-no-index.c b/diff-no-index.c
index f0b0010..fc1decd 100644
--- a/diff-no-index.c
+++ b/diff-no-index.c
@@ -224,12 +224,7 @@ void diff_no_index(struct rev_info *revs,
 		}
 	}
 
-	/*
-	 * If the user asked for our exit code then don't start a
-	 * pager or we would end up reporting its exit code instead.
-	 */
-	if (!DIFF_OPT_TST(&revs->diffopt, EXIT_WITH_STATUS))
-		setup_pager();
+	setup_diff_pager(&revs->diffopt);
 
 	if (prefix) {
 		int len = strlen(prefix);
-- 
1.7.11.rc2.4.g0b9de53

[PATCH 2/2] do not run pager with diff --no-index --quiet

[Jeff King]

There is no point in running a pager when --quiet is given,
since we are producing no output. The regular diff code path
handles this already, because --quiet implies --exit-code,
and we check for --exit-code when deciding not to run the
pager.

However, the "quiet implies exit-code" logic is done in
diff_setup_done, and the no-index code path sets up its
pager before running diff_setup_done, and misses this case.

We can fix this by reordering our initialization.
Currently we do:

  1. read command line arguments into diff_options

  2. Set pager if EXIT_CODE not requested

  3. always set EXIT_CODE, since we are emulating
     traditional diff

  4. call diff_setup_done

We can fix the problem by moving pager initialization (step
2) after step 4. But step 3 must come after step 2 (since we
want to know whether the _user_ requested --exit-code, not
whether we turned it on unconditionally). So we must move
both.

Signed-off-by: Jeff King <peff@peff.net>
---
We could also just check for QUICK in setup_diff_pager, which should be
a no-op for the regular diff case. But I think doing things in the same
order as regular diff could help prevent similar bugs in the future.

 diff-no-index.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/diff-no-index.c b/diff-no-index.c
index fc1decd..77667b8 100644
--- a/diff-no-index.c
+++ b/diff-no-index.c
@@ -224,8 +224,6 @@ void diff_no_index(struct rev_info *revs,
 		}
 	}
 
-	setup_diff_pager(&revs->diffopt);
-
 	if (prefix) {
 		int len = strlen(prefix);
 		const char *paths[3];
@@ -250,13 +248,15 @@ void diff_no_index(struct rev_info *revs,
 	if (!revs->diffopt.output_format)
 		revs->diffopt.output_format = DIFF_FORMAT_PATCH;
 
-	DIFF_OPT_SET(&revs->diffopt, EXIT_WITH_STATUS);
 	DIFF_OPT_SET(&revs->diffopt, NO_INDEX);
 
 	revs->max_count = -2;
 	if (diff_setup_done(&revs->diffopt) < 0)
 		die("diff_setup_done failed");
 
+	setup_diff_pager(&revs->diffopt);
+	DIFF_OPT_SET(&revs->diffopt, EXIT_WITH_STATUS);
+
 	if (queue_diff(&revs->diffopt, revs->diffopt.pathspec.raw[0],
 		       revs->diffopt.pathspec.raw[1]))
 		exit(1);
-- 
1.7.11.rc2.4.g0b9de53

Re: [PATCH 0/2] diff --no-index pager cleanups

[Junio C Hamano]

Jeff King <peff@peff.net> writes:

> While testing Tim's broken case, I noticed a few annoyances with the
> pager handling. These patches should clear them up.
>
>   [1/2]: fix pager.diff with diff --no-index
>   [2/2]: do not run pager with diff --no-index --quiet

Both look sane to me.  Thanks.