Merge branch 'jk/core-comment-string' into next

core.commentChar used to be limited to a single byte, but has been
updated to allow an arbitrary multi-byte sequence.

* jk/core-comment-string:
  config: add core.commentString
  config: allow multi-byte core.commentChar
  environment: drop comment_line_char compatibility macro
  wt-status: drop custom comment-char stringification
  sequencer: handle multi-byte comment characters when writing todo list
  find multi-byte comment chars in unterminated buffers
  find multi-byte comment chars in NUL-terminated strings
  prefer comment_line_str to comment_line_char for printing
  strbuf: accept a comment string for strbuf_add_commented_lines()
  strbuf: accept a comment string for strbuf_commented_addf()
  strbuf: accept a comment string for strbuf_stripspace()
  environment: store comment_line_char as a string
  strbuf: avoid shadowing global comment_line_char name
  commit: refactor base-case of adjust_comment_line_char()
  strbuf: avoid static variables in strbuf_add_commented_lines()
  strbuf: simplify comment-handling in add_lines() helper
  config: forbid newline as core.commentChar

Documentation/config/core.txt

@@ -520,13 +520,28 @@ core.editor::
 	`GIT_EDITOR` is not set.  See linkgit:git-var[1].
 
 core.commentChar::
+core.commentString::
 	Commands such as `commit` and `tag` that let you edit
-	messages consider a line that begins with this ASCII character
+	messages consider a line that begins with this character
 	commented, and removes them after the editor returns
 	(default '#').
 +
 If set to "auto", `git-commit` would select a character that is not
 the beginning character of any line in existing commit messages.
++
+Note that these two variables are aliases of each other, and in modern
+versions of Git you are free to use a string (e.g., `//` or `⁑⁕⁑`) with
+`commentChar`. Versions of Git prior to v2.45.0 will ignore
+`commentString` but will reject a value of `commentChar` that consists
+of more than a single ASCII byte. If you plan to use your config with
+older and newer versions of Git, you may want to specify both:
++
+    [core]
+    # single character for older versions
+    commentChar = "#"
+    # string for newer versions (which will override commentChar
+    # because it comes later in the file)
+    commentString = "//"
 
 core.filesRefLockTimeout::
 	The length of time, in milliseconds, to retry when trying to

add-patch.c

@@ -1105,26 +1105,26 @@ static int edit_hunk_manually(struct add_p_state *s, struct hunk *hunk)
 	size_t i;
 
 	strbuf_reset(&s->buf);
-	strbuf_commented_addf(&s->buf, comment_line_char,
+	strbuf_commented_addf(&s->buf, comment_line_str,
 			      _("Manual hunk edit mode -- see bottom for "
 				"a quick guide.\n"));
 	render_hunk(s, hunk, 0, 0, &s->buf);
-	strbuf_commented_addf(&s->buf, comment_line_char,
+	strbuf_commented_addf(&s->buf, comment_line_str,
 			      _("---\n"
 				"To remove '%c' lines, make them ' ' lines "
 				"(context).\n"
 				"To remove '%c' lines, delete them.\n"
-				"Lines starting with %c will be removed.\n"),
+				"Lines starting with %s will be removed.\n"),
 			      s->mode->is_reverse ? '+' : '-',
 			      s->mode->is_reverse ? '-' : '+',
-			      comment_line_char);
+			      comment_line_str);
-	strbuf_commented_addf(&s->buf, comment_line_char, "%s",
+	strbuf_commented_addf(&s->buf, comment_line_str, "%s",
 			      _(s->mode->edit_hunk_hint));
 	/*
 	 * TRANSLATORS: 'it' refers to the patch mentioned in the previous
 	 * messages.
 	 */
-	strbuf_commented_addf(&s->buf, comment_line_char,
+	strbuf_commented_addf(&s->buf, comment_line_str,
 			      _("If it does not apply cleanly, you will be "
 				"given an opportunity to\n"
 				"edit again.  If all lines of the hunk are "
@@ -1139,7 +1139,7 @@ static int edit_hunk_manually(struct add_p_state *s, struct hunk *hunk)
 	for (i = 0; i < s->buf.len; ) {
 		size_t next = find_next_line(&s->buf, i);
 
-		if (s->buf.buf[i] != comment_line_char)
+		if (!starts_with(s->buf.buf + i, comment_line_str))
 			strbuf_add(&s->plain, s->buf.buf + i, next - i);
 		i = next;
 	}

builtin/am.c

@@ -1290,7 +1290,7 @@ static int parse_mail(struct am_state *state, const char *mail)
 
 	strbuf_addstr(&msg, "\n\n");
 	strbuf_addbuf(&msg, &mi.log_message);
-	strbuf_stripspace(&msg, '\0');
+	strbuf_stripspace(&msg, NULL);
 
 	assert(!state->author_name);
 	state->author_name = strbuf_detach(&author_name, NULL);

builtin/branch.c

@@ -677,18 +677,18 @@ static int edit_branch_description(const char *branch_name)
 	exists = !read_branch_desc(&buf, branch_name);
 	if (!buf.len || buf.buf[buf.len-1] != '\n')
 		strbuf_addch(&buf, '\n');
-	strbuf_commented_addf(&buf, comment_line_char,
+	strbuf_commented_addf(&buf, comment_line_str,
 		    _("Please edit the description for the branch\n"
 		      "  %s\n"
-		      "Lines starting with '%c' will be stripped.\n"),
+		      "Lines starting with '%s' will be stripped.\n"),
-		    branch_name, comment_line_char);
+		    branch_name, comment_line_str);
 	write_file_buf(edit_description(), buf.buf, buf.len);
 	strbuf_reset(&buf);
 	if (launch_editor(edit_description(), &buf, NULL)) {
 		strbuf_release(&buf);
 		return -1;
 	}
-	strbuf_stripspace(&buf, comment_line_char);
+	strbuf_stripspace(&buf, comment_line_str);
 
 	strbuf_addf(&name, "branch.%s.description", branch_name);
 	if (buf.len || exists)

builtin/commit.c

@@ -685,9 +685,10 @@ static void adjust_comment_line_char(const struct strbuf *sb)
 	char *candidate;
 	const char *p;
 
-	comment_line_char = candidates[0];
+	if (!memchr(sb->buf, candidates[0], sb->len)) {
-	if (!memchr(sb->buf, comment_line_char, sb->len))
+		comment_line_str = xstrfmt("%c", candidates[0]);
 		return;
+	}
 
 	p = sb->buf;
 	candidate = strchr(candidates, *p);
@@ -706,7 +707,7 @@ static void adjust_comment_line_char(const struct strbuf *sb)
 	if (!*p)
 		die(_("unable to select a comment character that is not used\n"
 		      "in the current commit message"));
-	comment_line_char = *p;
+	comment_line_str = xstrfmt("%c", *p);
 }
 
 static void prepare_amend_commit(struct commit *commit, struct strbuf *sb,
@@ -889,7 +890,7 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 	s->hints = 0;
 
 	if (clean_message_contents)
-		strbuf_stripspace(&sb, '\0');
+		strbuf_stripspace(&sb, NULL);
 
 	if (signoff)
 		append_signoff(&sb, ignored_log_message_bytes(sb.buf, sb.len), 0);
@@ -909,18 +910,18 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 		struct ident_split ci, ai;
 		const char *hint_cleanup_all = allow_empty_message ?
 			_("Please enter the commit message for your changes."
-			  " Lines starting\nwith '%c' will be ignored.\n") :
+			  " Lines starting\nwith '%s' will be ignored.\n") :
 			_("Please enter the commit message for your changes."
-			  " Lines starting\nwith '%c' will be ignored, and an empty"
+			  " Lines starting\nwith '%s' will be ignored, and an empty"
 			  " message aborts the commit.\n");
 		const char *hint_cleanup_space = allow_empty_message ?
 			_("Please enter the commit message for your changes."
 			  " Lines starting\n"
-			  "with '%c' will be kept; you may remove them"
+			  "with '%s' will be kept; you may remove them"
 			  " yourself if you want to.\n") :
 			_("Please enter the commit message for your changes."
 			  " Lines starting\n"
-			  "with '%c' will be kept; you may remove them"
+			  "with '%s' will be kept; you may remove them"
 			  " yourself if you want to.\n"
 			  "An empty message aborts the commit.\n");
 		if (whence != FROM_COMMIT) {
@@ -943,12 +944,12 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 
 		fprintf(s->fp, "\n");
 		if (cleanup_mode == COMMIT_MSG_CLEANUP_ALL)
-			status_printf(s, GIT_COLOR_NORMAL, hint_cleanup_all, comment_line_char);
+			status_printf(s, GIT_COLOR_NORMAL, hint_cleanup_all, comment_line_str);
 		else if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS) {
 			if (whence == FROM_COMMIT)
 				wt_status_add_cut_line(s);
 		} else /* COMMIT_MSG_CLEANUP_SPACE, that is. */
-			status_printf(s, GIT_COLOR_NORMAL, hint_cleanup_space, comment_line_char);
+			status_printf(s, GIT_COLOR_NORMAL, hint_cleanup_space, comment_line_str);
 
 		/*
 		 * These should never fail because they come from our own

builtin/merge.c

@@ -822,7 +822,7 @@ static const char scissors_editor_comment[] =
 N_("An empty message aborts the commit.\n");
 
 static const char no_scissors_editor_comment[] =
-N_("Lines starting with '%c' will be ignored, and an empty message aborts\n"
+N_("Lines starting with '%s' will be ignored, and an empty message aborts\n"
    "the commit.\n");
 
 static void write_merge_heads(struct commit_list *);
@@ -853,16 +853,16 @@ static void prepare_to_commit(struct commit_list *remoteheads)
 		strbuf_addch(&msg, '\n');
 		if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS) {
 			wt_status_append_cut_line(&msg);
-			strbuf_commented_addf(&msg, comment_line_char, "\n");
+			strbuf_commented_addf(&msg, comment_line_str, "\n");
 		}
-		strbuf_commented_addf(&msg, comment_line_char,
+		strbuf_commented_addf(&msg, comment_line_str,
 				      _(merge_editor_comment));
 		if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS)
-			strbuf_commented_addf(&msg, comment_line_char,
+			strbuf_commented_addf(&msg, comment_line_str,
 					      _(scissors_editor_comment));
 		else
-			strbuf_commented_addf(&msg, comment_line_char,
+			strbuf_commented_addf(&msg, comment_line_str,
-				_(no_scissors_editor_comment), comment_line_char);
+				_(no_scissors_editor_comment), comment_line_str);
 	}
 	if (signoff)
 		append_signoff(&msg, ignored_log_message_bytes(msg.buf, msg.len), 0);

builtin/notes.c

@@ -179,7 +179,7 @@ static void write_commented_object(int fd, const struct object_id *object)
 
 	if (strbuf_read(&buf, show.out, 0) < 0)
 		die_errno(_("could not read 'show' output"));
-	strbuf_add_commented_lines(&cbuf, buf.buf, buf.len, comment_line_char);
+	strbuf_add_commented_lines(&cbuf, buf.buf, buf.len, comment_line_str);
 	write_or_die(fd, cbuf.buf, cbuf.len);
 
 	strbuf_release(&cbuf);
@@ -207,10 +207,10 @@ static void prepare_note_data(const struct object_id *object, struct note_data *
 			copy_obj_to_fd(fd, old_note);
 
 		strbuf_addch(&buf, '\n');
-		strbuf_add_commented_lines(&buf, "\n", strlen("\n"), comment_line_char);
+		strbuf_add_commented_lines(&buf, "\n", strlen("\n"), comment_line_str);
 		strbuf_add_commented_lines(&buf, _(note_template), strlen(_(note_template)),
-					   comment_line_char);
+					   comment_line_str);
-		strbuf_add_commented_lines(&buf, "\n", strlen("\n"), comment_line_char);
+		strbuf_add_commented_lines(&buf, "\n", strlen("\n"), comment_line_str);
 		write_or_die(fd, buf.buf, buf.len);
 
 		write_commented_object(fd, object);
@@ -223,7 +223,7 @@ static void prepare_note_data(const struct object_id *object, struct note_data *
 			die(_("please supply the note contents using either -m or -F option"));
 		}
 		if (d->stripspace)
-			strbuf_stripspace(&d->buf, comment_line_char);
+			strbuf_stripspace(&d->buf, comment_line_str);
 	}
 }
 
@@ -264,7 +264,7 @@ static void concat_messages(struct note_data *d)
 		if ((d->stripspace == UNSPECIFIED &&
 		     d->messages[i]->stripspace == STRIPSPACE) ||
 		    d->stripspace == STRIPSPACE)
-			strbuf_stripspace(&d->buf, 0);
+			strbuf_stripspace(&d->buf, NULL);
 		strbuf_reset(&msg);
 	}
 	strbuf_release(&msg);

builtin/rebase.c

@@ -204,7 +204,7 @@ static int edit_todo_file(unsigned flags)
 	if (strbuf_read_file(&todo_list.buf, todo_file, 0) < 0)
 		return error_errno(_("could not read '%s'."), todo_file);
 
-	strbuf_stripspace(&todo_list.buf, comment_line_char);
+	strbuf_stripspace(&todo_list.buf, comment_line_str);
 	res = edit_todo_list(the_repository, &todo_list, &new_todo, NULL, NULL, flags);
 	if (!res && todo_list_write_to_file(the_repository, &new_todo, todo_file,
 					    NULL, NULL, -1, flags & ~(TODO_LIST_SHORTEN_IDS)))

builtin/stripspace.c

@@ -13,7 +13,7 @@ static void comment_lines(struct strbuf *buf)
 	size_t len;
 
 	msg = strbuf_detach(buf, &len);
-	strbuf_add_commented_lines(buf, msg, len, comment_line_char);
+	strbuf_add_commented_lines(buf, msg, len, comment_line_str);
 	free(msg);
 }
 
@@ -59,7 +59,7 @@ int cmd_stripspace(int argc, const char **argv, const char *prefix)
 
 	if (mode == STRIP_DEFAULT || mode == STRIP_COMMENTS)
 		strbuf_stripspace(&buf,
-			  mode == STRIP_COMMENTS ? comment_line_char : '\0');
+			  mode == STRIP_COMMENTS ? comment_line_str : NULL);
 	else
 		comment_lines(&buf);
 

builtin/tag.c

@@ -193,11 +193,11 @@ static int do_sign(struct strbuf *buffer, struct object_id **compat_oid,
 
 static const char tag_template[] =
 	N_("\nWrite a message for tag:\n  %s\n"
-	"Lines starting with '%c' will be ignored.\n");
+	"Lines starting with '%s' will be ignored.\n");
 
 static const char tag_template_nocleanup[] =
 	N_("\nWrite a message for tag:\n  %s\n"
-	"Lines starting with '%c' will be kept; you may remove them"
+	"Lines starting with '%s' will be kept; you may remove them"
 	" yourself if you want to.\n");
 
 static int git_tag_config(const char *var, const char *value,
@@ -328,11 +328,11 @@ static void create_tag(const struct object_id *object, const char *object_ref,
 			struct strbuf buf = STRBUF_INIT;
 			strbuf_addch(&buf, '\n');
 			if (opt->cleanup_mode == CLEANUP_ALL)
-				strbuf_commented_addf(&buf, comment_line_char,
+				strbuf_commented_addf(&buf, comment_line_str,
-				      _(tag_template), tag, comment_line_char);
+				      _(tag_template), tag, comment_line_str);
 			else
-				strbuf_commented_addf(&buf, comment_line_char,
+				strbuf_commented_addf(&buf, comment_line_str,
-				      _(tag_template_nocleanup), tag, comment_line_char);
+				      _(tag_template_nocleanup), tag, comment_line_str);
 			write_or_die(fd, buf.buf, buf.len);
 			strbuf_release(&buf);
 		}
@@ -347,7 +347,7 @@ static void create_tag(const struct object_id *object, const char *object_ref,
 
 	if (opt->cleanup_mode != CLEANUP_NONE)
 		strbuf_stripspace(buf,
-		  opt->cleanup_mode == CLEANUP_ALL ? comment_line_char : '\0');
+		  opt->cleanup_mode == CLEANUP_ALL ? comment_line_str : NULL);
 
 	if (!opt->message_given && !buf->len)
 		die(_("no tag message?"));

builtin/worktree.c

@@ -657,7 +657,7 @@ static int can_use_local_refs(const struct add_opts *opts)
 			strbuf_add_real_path(&path, get_worktree_git_dir(NULL));
 			strbuf_addstr(&path, "/HEAD");
 			strbuf_read_file(&contents, path.buf, 64);
-			strbuf_stripspace(&contents, 0);
+			strbuf_stripspace(&contents, NULL);
 			strbuf_strip_suffix(&contents, "\n");
 
 			warning(_("HEAD points to an invalid (or orphaned) reference.\n"

commit.c

@@ -1928,7 +1928,8 @@ size_t ignored_log_message_bytes(const char *buf, size_t len)
 		else
 			next_line++;
 
-		if (buf[bol] == comment_line_char || buf[bol] == '\n') {
+		if (starts_with_mem(buf + bol, cutoff - bol, comment_line_str) ||
+		    buf[bol] == '\n') {
 			/* is this the first of the run of comments? */
 			if (!boc)
 				boc = bol;

config.c

@@ -1565,16 +1565,19 @@ static int git_default_core_config(const char *var, const char *value,
 	if (!strcmp(var, "core.editor"))
 		return git_config_string(&editor_program, var, value);
 
-	if (!strcmp(var, "core.commentchar")) {
+	if (!strcmp(var, "core.commentchar") ||
+	    !strcmp(var, "core.commentstring")) {
 		if (!value)
 			return config_error_nonbool(var);
 		else if (!strcasecmp(value, "auto"))
 			auto_comment_line_char = 1;
-		else if (value[0] && !value[1]) {
+		else if (value[0]) {
-			comment_line_char = value[0];
+			if (strchr(value, '\n'))
+				return error(_("%s cannot contain newline"), var);
+			comment_line_str = xstrdup(value);
 			auto_comment_line_char = 0;
 		} else
-			return error(_("core.commentChar should only be one ASCII character"));
+			return error(_("%s must have at least one character"), var);
 		return 0;
 	}
 

environment.c

@@ -110,7 +110,7 @@ int protect_ntfs = PROTECT_NTFS_DEFAULT;
  * The character that begins a commented line in user-editable file
  * that is subject to stripspace.
  */
-char comment_line_char = '#';
+const char *comment_line_str = "#";
 int auto_comment_line_char;
 
 /* Parallel index stat data preload? */

environment.h

@@ -8,7 +8,7 @@ struct strvec;
  * The character that begins a commented line in user-editable file
  * that is subject to stripspace.
  */
-extern char comment_line_char;
+extern const char *comment_line_str;
 extern int auto_comment_line_char;
 
 /*

fmt-merge-msg.c

@@ -321,7 +321,7 @@ static void credit_people(struct strbuf *out,
 	     skip_prefix(me, them->items->string, &me) &&
 	     starts_with(me, " <")))
 		return;
-	strbuf_addf(out, "\n%c %s ", comment_line_char, label);
+	strbuf_addf(out, "\n%s %s ", comment_line_str, label);
 	add_people_count(out, them);
 }
 
@@ -510,7 +510,7 @@ static void fmt_tag_signature(struct strbuf *tagbuf,
 	if (sig->len) {
 		strbuf_addch(tagbuf, '\n');
 		strbuf_add_commented_lines(tagbuf, sig->buf, sig->len,
-					   comment_line_char);
+					   comment_line_str);
 	}
 }
 
@@ -557,7 +557,7 @@ static void fmt_merge_msg_sigs(struct strbuf *out)
 				strbuf_add_commented_lines(&tagline,
 						origins.items[first_tag].string,
 						strlen(origins.items[first_tag].string),
-						comment_line_char);
+						comment_line_str);
 				strbuf_insert(&tagbuf, 0, tagline.buf,
 					      tagline.len);
 				strbuf_release(&tagline);
@@ -566,7 +566,7 @@ static void fmt_merge_msg_sigs(struct strbuf *out)
 			strbuf_add_commented_lines(&tagbuf,
 					origins.items[i].string,
 					strlen(origins.items[i].string),
-					comment_line_char);
+					comment_line_str);
 			fmt_tag_signature(&tagbuf, &sig, buf, len);
 		}
 		strbuf_release(&payload);

gpg-interface.c

@@ -586,8 +586,8 @@ static int verify_ssh_signed_buffer(struct signature_check *sigc,
 		}
 	}
 
-	strbuf_stripspace(&ssh_keygen_out, '\0');
+	strbuf_stripspace(&ssh_keygen_out, NULL);
-	strbuf_stripspace(&ssh_keygen_err, '\0');
+	strbuf_stripspace(&ssh_keygen_err, NULL);
 	/* Add stderr outputs to show the user actual ssh-keygen errors */
 	strbuf_add(&ssh_keygen_out, ssh_principals_err.buf, ssh_principals_err.len);
 	strbuf_add(&ssh_keygen_out, ssh_keygen_err.buf, ssh_keygen_err.len);

rebase-interactive.c

@@ -71,14 +71,14 @@ void append_todo_help(int command_count,
 
 	if (!edit_todo) {
 		strbuf_addch(buf, '\n');
-		strbuf_commented_addf(buf, comment_line_char,
+		strbuf_commented_addf(buf, comment_line_str,
 				      Q_("Rebase %s onto %s (%d command)",
 					 "Rebase %s onto %s (%d commands)",
 					 command_count),
 				      shortrevisions, shortonto, command_count);
 	}
 
-	strbuf_add_commented_lines(buf, msg, strlen(msg), comment_line_char);
+	strbuf_add_commented_lines(buf, msg, strlen(msg), comment_line_str);
 
 	if (get_missing_commit_check_level() == MISSING_COMMIT_CHECK_ERROR)
 		msg = _("\nDo not remove any line. Use 'drop' "
@@ -87,7 +87,7 @@ void append_todo_help(int command_count,
 		msg = _("\nIf you remove a line here "
 			 "THAT COMMIT WILL BE LOST.\n");
 
-	strbuf_add_commented_lines(buf, msg, strlen(msg), comment_line_char);
+	strbuf_add_commented_lines(buf, msg, strlen(msg), comment_line_str);
 
 	if (edit_todo)
 		msg = _("\nYou are editing the todo file "
@@ -98,7 +98,7 @@ void append_todo_help(int command_count,
 		msg = _("\nHowever, if you remove everything, "
 			"the rebase will be aborted.\n\n");
 
-	strbuf_add_commented_lines(buf, msg, strlen(msg), comment_line_char);
+	strbuf_add_commented_lines(buf, msg, strlen(msg), comment_line_str);
 }
 
 int edit_todo_list(struct repository *r, struct todo_list *todo_list,
@@ -130,7 +130,7 @@ int edit_todo_list(struct repository *r, struct todo_list *todo_list,
 	if (launch_sequence_editor(todo_file, &new_todo->buf, NULL))
 		return -2;
 
-	strbuf_stripspace(&new_todo->buf, comment_line_char);
+	strbuf_stripspace(&new_todo->buf, comment_line_str);
 	if (initial && new_todo->buf.len == 0)
 		return -3;
 

sequencer.c

@@ -678,15 +678,15 @@ void append_conflicts_hint(struct index_state *istate,
 	if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS) {
 		strbuf_addch(msgbuf, '\n');
 		wt_status_append_cut_line(msgbuf);
-		strbuf_addch(msgbuf, comment_line_char);
+		strbuf_addstr(msgbuf, comment_line_str);
 	}
 
 	strbuf_addch(msgbuf, '\n');
-	strbuf_commented_addf(msgbuf, comment_line_char, "Conflicts:\n");
+	strbuf_commented_addf(msgbuf, comment_line_str, "Conflicts:\n");
 	for (i = 0; i < istate->cache_nr;) {
 		const struct cache_entry *ce = istate->cache[i++];
 		if (ce_stage(ce)) {
-			strbuf_commented_addf(msgbuf, comment_line_char,
+			strbuf_commented_addf(msgbuf, comment_line_str,
 					      "\t%s\n", ce->name);
 			while (i < istate->cache_nr &&
 			       !strcmp(ce->name, istate->cache[i]->name))
@@ -1169,7 +1169,7 @@ void cleanup_message(struct strbuf *msgbuf,
 		strbuf_setlen(msgbuf, wt_status_locate_end(msgbuf->buf, msgbuf->len));
 	if (cleanup_mode != COMMIT_MSG_CLEANUP_NONE)
 		strbuf_stripspace(msgbuf,
-		  cleanup_mode == COMMIT_MSG_CLEANUP_ALL ? comment_line_char : '\0');
+		  cleanup_mode == COMMIT_MSG_CLEANUP_ALL ? comment_line_str : NULL);
 }
 
 /*
@@ -1201,7 +1201,7 @@ int template_untouched(const struct strbuf *sb, const char *template_file,
 		return 0;
 
 	strbuf_stripspace(&tmpl,
-	  cleanup_mode == COMMIT_MSG_CLEANUP_ALL ? comment_line_char : '\0');
+	  cleanup_mode == COMMIT_MSG_CLEANUP_ALL ? comment_line_str : NULL);
 	if (!skip_prefix(sb->buf, tmpl.buf, &start))
 		start = sb->buf;
 	strbuf_release(&tmpl);
@@ -1574,7 +1574,7 @@ static int try_to_commit(struct repository *r,
 
 	if (cleanup != COMMIT_MSG_CLEANUP_NONE)
 		strbuf_stripspace(msg,
-		  cleanup == COMMIT_MSG_CLEANUP_ALL ? comment_line_char : '\0');
+		  cleanup == COMMIT_MSG_CLEANUP_ALL ? comment_line_str : NULL);
 	if ((flags & EDIT_MSG) && message_is_empty(msg, cleanup)) {
 		res = 1; /* run 'git commit' to display error message */
 		goto out;
@@ -1796,6 +1796,8 @@ static const char *command_to_string(const enum todo_command command)
 {
 	if (command < TODO_COMMENT)
 		return todo_command_info[command].str;
+	if (command == TODO_COMMENT)
+		return comment_line_str;
 	die(_("unknown command: %d"), command);
 }
 
@@ -1803,7 +1805,7 @@ static char command_to_char(const enum todo_command command)
 {
 	if (command < TODO_COMMENT)
 		return todo_command_info[command].c;
-	return comment_line_char;
+	return 0;
 }
 
 static int is_noop(const enum todo_command command)
@@ -1857,7 +1859,7 @@ static int is_fixup_flag(enum todo_command command, unsigned flag)
 static void add_commented_lines(struct strbuf *buf, const void *str, size_t len)
 {
 	const char *s = str;
-	while (len > 0 && s[0] == comment_line_char) {
+	while (starts_with_mem(s, len, comment_line_str)) {
 		size_t count;
 		const char *n = memchr(s, '\n', len);
 		if (!n)
@@ -1868,7 +1870,7 @@ static void add_commented_lines(struct strbuf *buf, const void *str, size_t len)
 		s += count;
 		len -= count;
 	}
-	strbuf_add_commented_lines(buf, s, len, comment_line_char);
+	strbuf_add_commented_lines(buf, s, len, comment_line_str);
 }
 
 /* Does the current fixup chain contain a squash command? */
@@ -1963,11 +1965,11 @@ static int append_squash_message(struct strbuf *buf, const char *body,
 	     (starts_with(body, "squash!") || starts_with(body, "fixup!"))))
 		commented_len = commit_subject_length(body);
 
-	strbuf_addf(buf, "\n%c ", comment_line_char);
+	strbuf_addf(buf, "\n%s ", comment_line_str);
 	strbuf_addf(buf, _(nth_commit_msg_fmt),
 		    ++opts->current_fixup_count + 1);
 	strbuf_addstr(buf, "\n\n");
-	strbuf_add_commented_lines(buf, body, commented_len, comment_line_char);
+	strbuf_add_commented_lines(buf, body, commented_len, comment_line_str);
 	/* buf->buf may be reallocated so store an offset into the buffer */
 	fixup_off = buf->len;
 	strbuf_addstr(buf, body + commented_len);
@@ -2020,10 +2022,10 @@ static int update_squash_messages(struct repository *r,
 			return error(_("could not read '%s'"),
 				rebase_path_squash_msg());
 
-		eol = buf.buf[0] != comment_line_char ?
+		eol = !starts_with(buf.buf, comment_line_str) ?
 			buf.buf : strchrnul(buf.buf, '\n');
 
-		strbuf_addf(&header, "%c ", comment_line_char);
+		strbuf_addf(&header, "%s ", comment_line_str);
 		strbuf_addf(&header, _(combined_commit_msg_fmt),
 			    opts->current_fixup_count + 2);
 		strbuf_splice(&buf, 0, eol - buf.buf, header.buf, header.len);
@@ -2049,16 +2051,16 @@ static int update_squash_messages(struct repository *r,
 			repo_unuse_commit_buffer(r, head_commit, head_message);
 			return error(_("cannot write '%s'"), rebase_path_fixup_msg());
 		}
-		strbuf_addf(&buf, "%c ", comment_line_char);
+		strbuf_addf(&buf, "%s ", comment_line_str);
 		strbuf_addf(&buf, _(combined_commit_msg_fmt), 2);
-		strbuf_addf(&buf, "\n%c ", comment_line_char);
+		strbuf_addf(&buf, "\n%s ", comment_line_str);
 		strbuf_addstr(&buf, is_fixup_flag(command, flag) ?
 			      _(skip_first_commit_msg_str) :
 			      _(first_commit_msg_str));
 		strbuf_addstr(&buf, "\n\n");
 		if (is_fixup_flag(command, flag))
 			strbuf_add_commented_lines(&buf, body, strlen(body),
-						   comment_line_char);
+						   comment_line_str);
 		else
 			strbuf_addstr(&buf, body);
 
@@ -2073,12 +2075,12 @@ static int update_squash_messages(struct repository *r,
 	if (command == TODO_SQUASH || is_fixup_flag(command, flag)) {
 		res = append_squash_message(&buf, body, command, opts, flag);
 	} else if (command == TODO_FIXUP) {
-		strbuf_addf(&buf, "\n%c ", comment_line_char);
+		strbuf_addf(&buf, "\n%s ", comment_line_str);
 		strbuf_addf(&buf, _(skip_nth_commit_msg_fmt),
 			    ++opts->current_fixup_count + 1);
 		strbuf_addstr(&buf, "\n\n");
 		strbuf_add_commented_lines(&buf, body, strlen(body),
-					   comment_line_char);
+					   comment_line_str);
 	} else
 		return error(_("unknown command: %d"), command);
 	repo_unuse_commit_buffer(r, commit, message);
@@ -2579,7 +2581,7 @@ static int parse_insn_line(struct repository *r, struct todo_item *item,
 	/* left-trim */
 	bol += strspn(bol, " \t");
 
-	if (bol == eol || *bol == '\r' || *bol == comment_line_char) {
+	if (bol == eol || *bol == '\r' || starts_with_mem(bol, eol - bol, comment_line_str)) {
 		item->command = TODO_COMMENT;
 		item->commit = NULL;
 		item->arg_offset = bol - buf;
@@ -5682,8 +5684,8 @@ static int make_script_with_merges(struct pretty_print_context *pp,
 				    oid_to_hex(&commit->object.oid),
 				    oneline.buf);
 			if (is_empty)
-				strbuf_addf(&buf, " %c empty",
+				strbuf_addf(&buf, " %s empty",
-					    comment_line_char);
+					    comment_line_str);
 
 			FLEX_ALLOC_STR(entry, string, buf.buf);
 			oidcpy(&entry->entry.oid, &commit->object.oid);
@@ -5773,7 +5775,7 @@ static int make_script_with_merges(struct pretty_print_context *pp,
 		entry = oidmap_get(&state.commit2label, &commit->object.oid);
 
 		if (entry)
-			strbuf_addf(out, "\n%c Branch %s\n", comment_line_char, entry->string);
+			strbuf_addf(out, "\n%s Branch %s\n", comment_line_str, entry->string);
 		else
 			strbuf_addch(out, '\n');
 
@@ -5910,7 +5912,7 @@ int sequencer_make_script(struct repository *r, struct strbuf *out, int argc,
 			    oid_to_hex(&commit->object.oid));
 		pretty_print_commit(&pp, commit, out);
 		if (is_empty)
-			strbuf_addf(out, " %c empty", comment_line_char);
+			strbuf_addf(out, " %s empty", comment_line_str);
 		strbuf_addch(out, '\n');
 	}
 	if (skipped_commit)

strbuf.c

@@ -24,6 +24,17 @@ int istarts_with(const char *str, const char *prefix)
 			return 0;
 }
 
+int starts_with_mem(const char *str, size_t len, const char *prefix)
+{
+	const char *end = str + len;
+	for (; ; str++, prefix++) {
+		if (!*prefix)
+			return 1;
+		else if (str == end || *str != *prefix)
+			return 0;
+	}
+}
+
 int skip_to_optional_arg_default(const char *str, const char *prefix,
 				 const char **arg, const char *def)
 {
@@ -340,18 +351,17 @@ void strbuf_addf(struct strbuf *sb, const char *fmt, ...)
 }
 
 static void add_lines(struct strbuf *out,
-			const char *prefix1,
+			const char *prefix,
-			const char *prefix2,
+			const char *buf, size_t size,
-			const char *buf, size_t size)
+			int space_after_prefix)
 {
 	while (size) {
-		const char *prefix;
 		const char *next = memchr(buf, '\n', size);
 		next = next ? (next + 1) : (buf + size);
 
-		prefix = ((prefix2 && (buf[0] == '\n' || buf[0] == '\t'))
-			  ? prefix2 : prefix1);
 		strbuf_addstr(out, prefix);
+		if (space_after_prefix && buf[0] != '\n' && buf[0] != '\t')
+			strbuf_addch(out, ' ');
 		strbuf_add(out, buf, next - buf);
 		size -= next - buf;
 		buf = next;
@@ -360,19 +370,12 @@ static void add_lines(struct strbuf *out,
 }
 
 void strbuf_add_commented_lines(struct strbuf *out, const char *buf,
-				size_t size, char comment_line_char)
+				size_t size, const char *comment_prefix)
 {
-	static char prefix1[3];
+	add_lines(out, comment_prefix, buf, size, 1);
-	static char prefix2[2];
-
-	if (prefix1[0] != comment_line_char) {
-		xsnprintf(prefix1, sizeof(prefix1), "%c ", comment_line_char);
-		xsnprintf(prefix2, sizeof(prefix2), "%c", comment_line_char);
-	}
-	add_lines(out, prefix1, prefix2, buf, size);
 }
 
-void strbuf_commented_addf(struct strbuf *sb, char comment_line_char,
+void strbuf_commented_addf(struct strbuf *sb, const char *comment_prefix,
 			   const char *fmt, ...)
 {
 	va_list params;
@@ -383,7 +386,7 @@ void strbuf_commented_addf(struct strbuf *sb, char comment_line_char,
 	strbuf_vaddf(&buf, fmt, params);
 	va_end(params);
 
-	strbuf_add_commented_lines(sb, buf.buf, buf.len, comment_line_char);
+	strbuf_add_commented_lines(sb, buf.buf, buf.len, comment_prefix);
 	if (incomplete_line)
 		sb->buf[--sb->len] = '\0';
 
@@ -770,7 +773,7 @@ ssize_t strbuf_read_file(struct strbuf *sb, const char *path, size_t hint)
 void strbuf_add_lines(struct strbuf *out, const char *prefix,
 		      const char *buf, size_t size)
 {
-	add_lines(out, prefix, NULL, buf, size);
+	add_lines(out, prefix, buf, size, 0);
 }
 
 void strbuf_addstr_xml_quoted(struct strbuf *buf, const char *s)
@@ -1025,10 +1028,10 @@ static size_t cleanup(char *line, size_t len)
  *
  * If last line does not have a newline at the end, one is added.
  *
- * Pass a non-NUL comment_line_char to skip every line starting
+ * Pass a non-NULL comment_prefix to skip every line starting
  * with it.
  */
-void strbuf_stripspace(struct strbuf *sb, char comment_line_char)
+void strbuf_stripspace(struct strbuf *sb, const char *comment_prefix)
 {
 	size_t empties = 0;
 	size_t i, j, len, newlen;
@@ -1041,8 +1044,8 @@ void strbuf_stripspace(struct strbuf *sb, char comment_line_char)
 		eol = memchr(sb->buf + i, '\n', sb->len - i);
 		len = eol ? eol - (sb->buf + i) + 1 : sb->len - i;
 
-		if (comment_line_char && len &&
+		if (comment_prefix && len &&
-		    sb->buf[i] == comment_line_char) {
+		    starts_with(sb->buf + i, comment_prefix)) {
 			newlen = 0;
 			continue;
 		}

strbuf.h

@@ -288,7 +288,7 @@ void strbuf_splice(struct strbuf *sb, size_t pos, size_t len,
  */
 void strbuf_add_commented_lines(struct strbuf *out,
 				const char *buf, size_t size,
-				char comment_line_char);
+				const char *comment_prefix);
 
 
 /**
@@ -384,7 +384,7 @@ void strbuf_addf(struct strbuf *sb, const char *fmt, ...);
  * blank to the buffer.
  */
 __attribute__((format (printf, 3, 4)))
-void strbuf_commented_addf(struct strbuf *sb, char comment_line_char, const char *fmt, ...);
+void strbuf_commented_addf(struct strbuf *sb, const char *comment_prefix, const char *fmt, ...);
 
 __attribute__((format (printf,2,0)))
 void strbuf_vaddf(struct strbuf *sb, const char *fmt, va_list ap);
@@ -518,11 +518,11 @@ int strbuf_getcwd(struct strbuf *sb);
 int strbuf_normalize_path(struct strbuf *sb);
 
 /**
- * Strip whitespace from a buffer. If comment_line_char is non-NUL,
+ * Strip whitespace from a buffer. If comment_prefix is non-NULL,
  * then lines beginning with that character are considered comments,
  * thus removed.
  */
-void strbuf_stripspace(struct strbuf *buf, char comment_line_char);
+void strbuf_stripspace(struct strbuf *buf, const char *comment_prefix);
 
 static inline int strbuf_strip_suffix(struct strbuf *sb, const char *suffix)
 {
@@ -678,6 +678,7 @@ char *xstrfmt(const char *fmt, ...);
 
 int starts_with(const char *str, const char *prefix);
 int istarts_with(const char *str, const char *prefix);
+int starts_with_mem(const char *str, size_t len, const char *prefix);
 
 /*
  * If the string "str" is the same as the string in "prefix", then the "arg"

t/t0030-stripspace.sh

@@ -401,6 +401,21 @@ test_expect_success 'strip comments with changed comment char' '
 	test -z "$(echo "; comment" | git -c core.commentchar=";" stripspace -s)"
 '
 
+test_expect_success 'strip comments with changed comment string' '
+	test ! -z "$(echo "// comment" | git -c core.commentchar=// stripspace)" &&
+	test -z "$(echo "// comment" | git -c core.commentchar="//" stripspace -s)"
+'
+
+test_expect_success 'newline as commentchar is forbidden' '
+	test_must_fail git -c core.commentChar="$LF" stripspace -s 2>err &&
+	grep "core.commentchar cannot contain newline" err
+'
+
+test_expect_success 'empty commentchar is forbidden' '
+	test_must_fail git -c core.commentchar= stripspace -s 2>err &&
+	grep "core.commentchar must have at least one character" err
+'
+
 test_expect_success '-c with single line' '
 	printf "# foo\n" >expect &&
 	printf "foo" | git stripspace -c >actual &&

t/t7507-commit-verbose.sh

@@ -101,6 +101,16 @@ test_expect_success 'verbose diff is stripped out with set core.commentChar' '
 	test_grep "Aborting commit due to empty commit message." err
 '
 
+test_expect_success 'verbose diff is stripped with multi-byte comment char' '
+	(
+		GIT_EDITOR=cat &&
+		export GIT_EDITOR &&
+		test_must_fail git -c core.commentchar="foo>" commit -a -v >out 2>err
+	) &&
+	grep "^foo> " out &&
+	test_grep "Aborting commit due to empty commit message." err
+'
+
 test_expect_success 'status does not verbose without --verbose' '
 	git status >actual &&
 	! grep "^diff --git" actual

t/t7508-status.sh

@@ -1415,7 +1415,9 @@ test_expect_success "status (core.commentchar with submodule summary)" '
 
 test_expect_success "status (core.commentchar with two chars with submodule summary)" '
 	test_config core.commentchar ";;" &&
-	test_must_fail git -c status.displayCommentPrefix=true status
+	sed "s/^/;/" <expect >expect.double &&
+	git -c status.displayCommentPrefix=true status >output &&
+	test_cmp expect.double output
 '
 
 test_expect_success "--ignore-submodules=all suppresses submodule summary" '

trailer.c

@@ -871,7 +871,7 @@ static size_t find_trailer_block_start(const char *buf, size_t len)
 
 	/* The first paragraph is the title and cannot be trailers */
 	for (s = buf; s < buf + len; s = next_line(s)) {
-		if (s[0] == comment_line_char)
+		if (starts_with_mem(s, buf + len - s, comment_line_str))
 			continue;
 		if (is_blank_line(s))
 			break;
@@ -891,7 +891,7 @@ static size_t find_trailer_block_start(const char *buf, size_t len)
 		const char **p;
 		ssize_t separator_pos;
 
-		if (bol[0] == comment_line_char) {
+		if (starts_with_mem(bol, buf + len - bol, comment_line_str)) {
 			non_trailer_lines += possible_continuation_lines;
 			possible_continuation_lines = 0;
 			continue;
@@ -1002,7 +1002,7 @@ void parse_trailers(const struct process_trailer_options *opts,
 	for (i = 0; i < info->trailer_nr; i++) {
 		int separator_pos;
 		char *trailer = info->trailers[i];
-		if (trailer[0] == comment_line_char)
+		if (starts_with(trailer, comment_line_str))
 			continue;
 		separator_pos = find_separator(trailer, separators);
 		if (separator_pos >= 1) {

wt-status.c

@@ -70,7 +70,7 @@ static void status_vprintf(struct wt_status *s, int at_bol, const char *color,
 	strbuf_vaddf(&sb, fmt, ap);
 	if (!sb.len) {
 		if (s->display_comment_prefix) {
-			strbuf_addch(&sb, comment_line_char);
+			strbuf_addstr(&sb, comment_line_str);
 			if (!trail)
 				strbuf_addch(&sb, ' ');
 		}
@@ -85,7 +85,7 @@ static void status_vprintf(struct wt_status *s, int at_bol, const char *color,
 
 		strbuf_reset(&linebuf);
 		if (at_bol && s->display_comment_prefix) {
-			strbuf_addch(&linebuf, comment_line_char);
+			strbuf_addstr(&linebuf, comment_line_str);
 			if (*line != '\n' && *line != '\t')
 				strbuf_addch(&linebuf, ' ');
 		}
@@ -1028,7 +1028,7 @@ static void wt_longstatus_print_submodule_summary(struct wt_status *s, int uncom
 	if (s->display_comment_prefix) {
 		size_t len;
 		summary_content = strbuf_detach(&summary, &len);
-		strbuf_add_commented_lines(&summary, summary_content, len, comment_line_char);
+		strbuf_add_commented_lines(&summary, summary_content, len, comment_line_str);
 		free(summary_content);
 	}
 
@@ -1090,7 +1090,7 @@ size_t wt_status_locate_end(const char *s, size_t len)
 	const char *p;
 	struct strbuf pattern = STRBUF_INIT;
 
-	strbuf_addf(&pattern, "\n%c %s", comment_line_char, cut_line);
+	strbuf_addf(&pattern, "\n%s %s", comment_line_str, cut_line);
 	if (starts_with(s, pattern.buf + 1))
 		len = 0;
 	else if ((p = strstr(s, pattern.buf))) {
@@ -1106,8 +1106,8 @@ void wt_status_append_cut_line(struct strbuf *buf)
 {
 	const char *explanation = _("Do not modify or remove the line above.\nEverything below it will be ignored.");
 
-	strbuf_commented_addf(buf, comment_line_char, "%s", cut_line);
+	strbuf_commented_addf(buf, comment_line_str, "%s", cut_line);
-	strbuf_add_commented_lines(buf, explanation, strlen(explanation), comment_line_char);
+	strbuf_add_commented_lines(buf, explanation, strlen(explanation), comment_line_str);
 }
 
 void wt_status_add_cut_line(struct wt_status *s)
@@ -1183,8 +1183,6 @@ static void wt_longstatus_print_tracking(struct wt_status *s)
 	struct strbuf sb = STRBUF_INIT;
 	const char *cp, *ep, *branch_name;
 	struct branch *branch;
-	char comment_line_string[3];
-	int i;
 	uint64_t t_begin = 0;
 
 	assert(s->branch && !s->is_initial);
@@ -1209,20 +1207,15 @@ static void wt_longstatus_print_tracking(struct wt_status *s)
 		}
 	}
 
-	i = 0;
-	if (s->display_comment_prefix) {
-		comment_line_string[i++] = comment_line_char;
-		comment_line_string[i++] = ' ';
-	}
-	comment_line_string[i] = '\0';
-
 	for (cp = sb.buf; (ep = strchr(cp, '\n')) != NULL; cp = ep + 1)
 		color_fprintf_ln(s->fp, color(WT_STATUS_HEADER, s),
-				 "%s%.*s", comment_line_string,
+				 "%s%s%.*s",
+				 s->display_comment_prefix ? comment_line_str : "",
+				 s->display_comment_prefix ? " " : "",
 				 (int)(ep - cp), cp);
 	if (s->display_comment_prefix)
-		color_fprintf_ln(s->fp, color(WT_STATUS_HEADER, s), "%c",
+		color_fprintf_ln(s->fp, color(WT_STATUS_HEADER, s), "%s",
-				 comment_line_char);
+				 comment_line_str);
 	else
 		fputs("\n", s->fp);
 	strbuf_release(&sb);
@@ -1389,7 +1382,7 @@ static int read_rebase_todolist(const char *fname, struct string_list *lines)
 			  git_path("%s", fname));
 	}
 	while (!strbuf_getline_lf(&line, f)) {
-		if (line.len && line.buf[0] == comment_line_char)
+		if (starts_with(line.buf, comment_line_str))
 			continue;
 		strbuf_trim(&line);
 		if (!line.len)