sequencer: make it clearer that commit descriptions are just comments

Every once in a while, users report that editing the commit summaries
in the todo list does not get reflected in the rebase operation,
suggesting that users are (a) only using one-line commit messages, and
(b) not understanding that the commit summaries are merely helpful
comments to help them find the right hashes.

It may be difficult to correct users' poor commit messages, but we can
at least try to make it clearer that the commit summaries are not
directives of some sort by inserting a comment character.  Hopefully
that leads to them looking a little further and noticing the hints at
the bottom to use 'reword' or 'edit' directives.

Yes, this change may look funny at first since it hardcodes '#' rather
than using comment_line_str.  However:

  * comment_line_str exists to allow disambiguation between lines in
    a commit message and lines that are instructions to users editing
    the commit message.  No such disambiguation is needed for these
    comments that occur on the same line after existing directives
  * the exact "comment" character(s) on regular pick lines used aren't
    actually important; I could have used anything, including completely
    random variable length text for each line and it'd work because we
    ignore everything after 'pick' and the hash.
  * The whole point of this change is to signal to users that they
    should NOT be editing any part of the line after the hash (and if
    they do so, their edits will be ignored), while the whole point of
    comment_line_str is to allow highly flexible editing.  So making
    it more general by using comment_line_str actually feels
    counterproductive.
  * The character for merge directives absolutely must be '#'; that
    has been deeply hardcoded for a long time (see below), and will
    break if some other comment character is used instead.  In a
    desire to have pick and merge directives be similar, I use the
    same comment character for both.
  * Perhaps merge directives could be fixed to not be inflexible about
    the comment character used, if someone feels highly motivated, but
    I think that should be done in a separate follow-on patch.

Here are (some of?) the locations where '#' has already been hardcoded
for a long time for merges:

  1) In check_label_or_ref_arg():
	case TODO_LABEL:
		/*
		 * '#' is not a valid label as the merge command uses it to
		 * separate merge parents from the commit subject.
		 */

  2) In do_merge():

	/*
	 * For octopus merges, the arg starts with the list of revisions to be
	 * merged. The list is optionally followed by '#' and the oneline.
	 */
	merge_arg_len = oneline_offset = arg_len;
	for (p = arg; p - arg < arg_len; p += strspn(p, " \t\n")) {
		if (!*p)
			break;
		if (*p == '#' && (!p[1] || isspace(p[1]))) {

  3) In label_oid():

		if ((buf->len == the_hash_algo->hexsz &&
		     !get_oid_hex(label, &dummy)) ||
		    (buf->len == 1 && *label == '#') ||
		    hashmap_get_from_hash(&state->labels,
					  strihash(label), label)) {
			/*
			 * If the label already exists, or if the label is a
			 * valid full OID, or the label is a '#' (which we use
			 * as a separator between merge heads and oneline), we
			 * append a dash and a number to make it unique.
			 */

Signed-off-by: Elijah Newren <[email protected]>

Author: newren

sequencer.c

@@ -5901,11 +5901,11 @@ static int make_script_with_merges(struct pretty_print_context *pp,
 
 		/* Create a label from the commit message */
 		strbuf_reset(&label_from_message);
-		if (skip_prefix(oneline.buf, "Merge ", &p1) &&
+		if (skip_prefix(oneline.buf, "# Merge ", &p1) &&
 		    (p1 = strchr(p1, '\'')) &&
 		    (p2 = strchr(++p1, '\'')))
 			strbuf_add(&label_from_message, p1, p2 - p1);
-		else if (skip_prefix(oneline.buf, "Merge pull request ",
+		else if (skip_prefix(oneline.buf, "# Merge pull request ",
 				     &p1) &&
 			 (p1 = strstr(p1, " from ")))
 			strbuf_addstr(&label_from_message, p1 + strlen(" from "));
@@ -5940,7 +5940,7 @@ static int make_script_with_merges(struct pretty_print_context *pp,
 
 			strbuf_addstr(&buf, label_oid(oid, label, &state));
 		}
-		strbuf_addf(&buf, " # %s", oneline.buf);
+		strbuf_addf(&buf, " %s", oneline.buf);
 
 		FLEX_ALLOC_STR(entry, string, buf.buf);
 		oidcpy(&entry->entry.oid, &commit->object.oid);
@@ -6022,7 +6022,7 @@ static int make_script_with_merges(struct pretty_print_context *pp,
 			else {
 				strbuf_reset(&oneline);
 				pretty_print_commit(pp, commit, &oneline);
-				strbuf_addf(out, "%s %s # %s\n",
+				strbuf_addf(out, "%s %s %s\n",
 					    cmd_reset, to, oneline.buf);
 			}
 		}
@@ -6090,8 +6090,14 @@ int sequencer_make_script(struct repository *r, struct strbuf *out, int argc,
 	git_config_get_string("rebase.instructionFormat", &format);
 	if (!format || !*format) {
 		free(format);
-		format = xstrdup("%s");
+		format = xstrdup("# %s");
 	}
+	if (*format != '#') {
+		char *temp = format;
+		format = xstrfmt("# %s", temp);
+		free(temp);
+	}
+
 	get_commit_format(format, &revs);
 	free(format);
 	pp.fmt = revs.commit_format;

t/t3404-rebase-interactive.sh

@@ -1468,7 +1468,7 @@ test_expect_success 'rebase -i respects rebase.missingCommitsCheck = warn' '
 	cat >expect <<-EOF &&
 	Warning: some commits may have been dropped accidentally.
 	Dropped commits (newer to older):
-	 - $(git rev-list --pretty=oneline --abbrev-commit -1 primary)
+	 - $(git log --format="%h # %s" -1 primary)
 	To avoid this message, use "drop" to explicitly remove a commit.
 	EOF
 	test_config rebase.missingCommitsCheck warn &&
@@ -1486,8 +1486,8 @@ test_expect_success 'rebase -i respects rebase.missingCommitsCheck = error' '
 	cat >expect <<-EOF &&
 	Warning: some commits may have been dropped accidentally.
 	Dropped commits (newer to older):
-	 - $(git rev-list --pretty=oneline --abbrev-commit -1 primary)
-	 - $(git rev-list --pretty=oneline --abbrev-commit -1 primary~2)
+	 - $(git log --format="%h # %s" -1 primary)
+	 - $(git log --format="%h # %s" -1 primary~2)
 	To avoid this message, use "drop" to explicitly remove a commit.
 
 	Use '\''git config rebase.missingCommitsCheck'\'' to change the level of warnings.
@@ -1530,11 +1530,11 @@ test_expect_success 'rebase --edit-todo respects rebase.missingCommitsCheck = ig
 test_expect_success 'rebase --edit-todo respects rebase.missingCommitsCheck = warn' '
 	cat >expect <<-EOF &&
 	error: invalid command '\''pickled'\''
-	error: invalid line 1: pickled $(git rev-list --pretty=oneline --abbrev-commit -1 primary~4)
+	error: invalid line 1: pickled $(git log --format="%h # %s" -1 primary~4)
 	Warning: some commits may have been dropped accidentally.
 	Dropped commits (newer to older):
-	 - $(git rev-list --pretty=oneline --abbrev-commit -1 primary)
-	 - $(git rev-list --pretty=oneline --abbrev-commit -1 primary~4)
+	 - $(git log --format="%h # %s" -1 primary)
+	 - $(git log --format="%h # %s" -1 primary~4)
 	To avoid this message, use "drop" to explicitly remove a commit.
 	EOF
 	head -n5 expect >expect.2 &&
@@ -1565,11 +1565,11 @@ test_expect_success 'rebase --edit-todo respects rebase.missingCommitsCheck = wa
 test_expect_success 'rebase --edit-todo respects rebase.missingCommitsCheck = error' '
 	cat >expect <<-EOF &&
 	error: invalid command '\''pickled'\''
-	error: invalid line 1: pickled $(git rev-list --pretty=oneline --abbrev-commit -1 primary~4)
+	error: invalid line 1: pickled $(git log --format="%h # %s" -1 primary~4)
 	Warning: some commits may have been dropped accidentally.
 	Dropped commits (newer to older):
-	 - $(git rev-list --pretty=oneline --abbrev-commit -1 primary)
-	 - $(git rev-list --pretty=oneline --abbrev-commit -1 primary~4)
+	 - $(git log --format="%h # %s" -1 primary)
+	 - $(git log --format="%h # %s" -1 primary~4)
 	To avoid this message, use "drop" to explicitly remove a commit.
 
 	Use '\''git config rebase.missingCommitsCheck'\'' to change the level of warnings.
@@ -1642,11 +1642,11 @@ test_expect_success 'respects rebase.abbreviateCommands with fixup, squash and e
 	test_commit "fixup! first" file2.txt "first line again" first_fixup &&
 	test_commit "squash! second" file1.txt "another line here" second_squash &&
 	cat >expected <<-EOF &&
-	p $(git rev-list --abbrev-commit -1 first) first
-	f $(git rev-list --abbrev-commit -1 first_fixup) fixup! first
+	p $(git rev-list --abbrev-commit -1 first) # first
+	f $(git rev-list --abbrev-commit -1 first_fixup) # fixup! first
 	x git show HEAD
-	p $(git rev-list --abbrev-commit -1 second) second
-	s $(git rev-list --abbrev-commit -1 second_squash) squash! second
+	p $(git rev-list --abbrev-commit -1 second) # second
+	s $(git rev-list --abbrev-commit -1 second_squash) # squash! second
 	x git show HEAD
 	EOF
 	git checkout abbrevcmd &&
@@ -1665,7 +1665,7 @@ test_expect_success 'static check of bad command' '
 		set_fake_editor &&
 		test_must_fail env FAKE_LINES="1 2 3 bad 4 5" \
 		git rebase -i --root 2>actual &&
-		test_grep "pickled $(git rev-list --oneline -1 primary~1)" \
+		test_grep "pickled $(git log --format="%h # %s" -1 primary~1)" \
 				actual &&
 		test_grep "You can fix this with .git rebase --edit-todo.." \
 				actual &&
@@ -1865,15 +1865,15 @@ test_expect_success '--update-refs adds label and update-ref commands' '
 		set_cat_todo_editor &&
 
 		cat >expect <<-EOF &&
-		pick $(git log -1 --format=%h J) J
-		fixup $(git log -1 --format=%h update-refs) fixup! J # empty
+		pick $(git log -1 --format=%h J) # J
+		fixup $(git log -1 --format=%h update-refs) # fixup! J # empty
 		update-ref refs/heads/second
 		update-ref refs/heads/first
-		pick $(git log -1 --format=%h K) K
-		pick $(git log -1 --format=%h L) L
-		fixup $(git log -1 --format=%h is-not-reordered) fixup! L # empty
+		pick $(git log -1 --format=%h K) # K
+		pick $(git log -1 --format=%h L) # L
+		fixup $(git log -1 --format=%h is-not-reordered) # fixup! L # empty
 		update-ref refs/heads/third
-		pick $(git log -1 --format=%h M) M
+		pick $(git log -1 --format=%h M) # M
 		update-ref refs/heads/no-conflict-branch
 		update-ref refs/heads/is-not-reordered
 		update-ref refs/heads/shared-tip
@@ -1905,19 +1905,19 @@ test_expect_success '--update-refs adds commands with --rebase-merges' '
 		cat >expect <<-EOF &&
 		label onto
 		reset onto
-		pick $(git log -1 --format=%h branch2~1) F
-		pick $(git log -1 --format=%h branch2) I
+		pick $(git log -1 --format=%h branch2~1) # F
+		pick $(git log -1 --format=%h branch2) # I
 		update-ref refs/heads/branch2
 		label branch2
 		reset onto
-		pick $(git log -1 --format=%h refs/heads/second) J
+		pick $(git log -1 --format=%h refs/heads/second) # J
 		update-ref refs/heads/second
 		update-ref refs/heads/first
-		pick $(git log -1 --format=%h refs/heads/third~1) K
-		pick $(git log -1 --format=%h refs/heads/third) L
-		fixup $(git log -1 --format=%h update-refs-with-merge) fixup! L # empty
+		pick $(git log -1 --format=%h refs/heads/third~1) # K
+		pick $(git log -1 --format=%h refs/heads/third) # L
+		fixup $(git log -1 --format=%h update-refs-with-merge) # fixup! L # empty
 		update-ref refs/heads/third
-		pick $(git log -1 --format=%h HEAD~2) M
+		pick $(git log -1 --format=%h HEAD~2) # M
 		update-ref refs/heads/no-conflict-branch
 		merge -C $(git log -1 --format=%h HEAD~1) branch2 # merge
 		update-ref refs/heads/merge-branch

t/t3415-rebase-autosquash.sh

@@ -257,8 +257,8 @@ test_expect_success 'auto squash of fixup commit that matches branch name which
 	GIT_SEQUENCE_EDITOR="cat >tmp" git rebase --autosquash -i HEAD^^ &&
 	sed -ne "/^[^#]/{s/[0-9a-f]\{7,\}/HASH/g;p;}" tmp >actual &&
 	cat <<-EOF >expect &&
-	pick HASH second commit
-	pick HASH fixup! self-cycle # empty
+	pick HASH # second commit
+	pick HASH # fixup! self-cycle # empty
 	EOF
 	test_cmp expect actual
 '
@@ -311,10 +311,10 @@ test_auto_fixup_fixup () {
 		parent2=$(git rev-parse --short HEAD^^) &&
 		parent3=$(git rev-parse --short HEAD^^^) &&
 		cat >expected <<-EOF &&
-		pick $parent3 first commit
-		$1 $parent1 $1! first
-		$1 $head $1! $2! first
-		pick $parent2 second commit
+		pick $parent3 # first commit
+		$1 $parent1 # $1! first
+		$1 $head # $1! $2! first
+		pick $parent2 # second commit
 		EOF
 		test_cmp expected actual
 	) &&
@@ -389,7 +389,7 @@ test_expect_success 'autosquash with empty custom instructionFormat' '
 		set_cat_todo_editor &&
 		test_must_fail git -c rebase.instructionFormat= \
 			rebase --autosquash  --force-rebase -i HEAD^ >actual &&
-		git log -1 --format="pick %h %s" >expect &&
+		git log -1 --format="pick %h # %s" >expect &&
 		test_cmp expect actual
 	)
 '

t/t3430-rebase-merges.sh

@@ -106,18 +106,18 @@ test_expect_success 'generate correct todo list' '
 	label onto
 
 	reset onto
-	pick $b B
+	pick $b # B
 	label first
 
 	reset onto
-	pick $c C
+	pick $c # C
 	label branch-point
-	pick $f F
-	pick $g G
+	pick $f # F
+	pick $g # G
 	label second
 
 	reset branch-point # C
-	pick $d D
+	pick $d # D
 	merge -C $e first # E
 	merge -C $h second # H
 

t/t5520-pull.sh

@@ -813,7 +813,7 @@ test_expect_success 'git pull --rebase does not reapply old patches' '
 		cd dst &&
 		test_must_fail git pull --rebase &&
 		cat .git/rebase-merge/done .git/rebase-merge/git-rebase-todo >work &&
-		grep -v -e \# -e ^$ work >patches &&
+		grep -v -e ^\# -e ^$ work >patches &&
 		test_line_count = 1 patches &&
 		rm -f work
 	)