Re: [RFC PATCH] commit -v: strip diffs and submodule shortlogs from the commit message

When using the '-v' option of "git commit" the diff added to the commit
message temporarily for editing is stripped off after the user exited the
editor by searching for "\ndiff --git " and truncating the commmit message
there if it is found. But this approach has two problems: when the commit
message itself contains a line starting with "diff --git" it will be
truncated there prematurely. And when the "diff.submodule" setting is set
to "log", the diff may start with "Submodule <hash1>..<hash2>", which will
be left in the commit message while it shouldn't.

Fix that by introducing a special scissor separator line starting with the
comment character '#' followed by a line describing what it is for. The
scissor line is used to reliably detect the start of the diff so it can be
chopped off from the commit message, no matter what the user enters there.
Turn a known test failure fixed by this change into a successful test and
add another one for a diff starting with a submodule log.

Reported-by: Ari Pollak <redacted>
Signed-off-by: Jens Lehmann <redacted>
---

 builtin/commit.c          |  6 +++---
 t/t7507-commit-verbose.sh | 15 ++++++++++++++-
 wt-status.c               |  4 ++++
 wt-status.h               |  2 ++
 4 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/builtin/commit.c b/builtin/commit.c
index 6ab4605..091a6e7 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c

@@ -1602,9 +1602,9 @@ int cmd_commit(int argc, const char **argv, const char *prefix)

        /* Truncate the message just before the diff, if any. */
        if (verbose) {
-               p = strstr(sb.buf, "\ndiff --git ");
-               if (p != NULL)
-                       strbuf_setlen(&sb, p - sb.buf + 1);
+               p = strstr(sb.buf, wt_status_diff_divider);

+               if ((p != NULL) && (p > sb.buf) && (p[-1] == '\n'))
+                       strbuf_setlen(&sb, p - sb.buf);
        }

        if (cleanup_mode != CLEANUP_NONE)

diff --git a/wt-status.c b/wt-status.c
index b4e44ba..a3f7115 100644
--- a/wt-status.c
+++ b/wt-status.c

@@ -16,6 +16,8 @@
 #include "column.h"
 #include "strbuf.h"

+const char wt_status_diff_divider[] = "# -----------------------------------8<-----------------------------------\n";
+
 static char default_wt_status_colors[][COLOR_MAXLEN] = {
        GIT_COLOR_NORMAL, /* WT_STATUS_HEADER */
        GIT_COLOR_GREEN,  /* WT_STATUS_UPDATED */

@@ -791,6 +793,8 @@ static void wt_status_print_verbose(struct wt_status *s)
         */
        if (s->fp != stdout)
                rev.diffopt.use_color = 0;
+       fprintf(s->fp, wt_status_diff_divider);
+       fprintf(s->fp, _("# The diff below will be removed when keeping the previous line.\n"));
        run_diff_index(&rev, 1);
 }

diff --git a/wt-status.h b/wt-status.h
index 6c29e6f..cd2709f 100644
--- a/wt-status.h
+++ b/wt-status.h

@@ -91,6 +91,8 @@ struct wt_status_state {
        unsigned char cherry_pick_head_sha1[20];
 };

+const char wt_status_diff_divider[];
+
 void wt_status_prepare(struct wt_status *s);
 void wt_status_print(struct wt_status *s);
 void wt_status_collect(struct wt_status *s);
--