alias: support non-alphanumeric names via subsection syntax

Git alias names are limited to ASCII alphanumeric characters and
dashes because aliases are implemented as config variable names.
This prevents aliases being created in languages using characters outside that range.

Add support for arbitrary alias names by using config subsections:

    [alias "förgrena"]
        command = branch

The subsection name is matched as-is (case-sensitive byte comparison),
while the existing definition without a subsection (e.g.,
"[alias] co = checkout") remains case-insensitive for backward
compatibility. This uses existing config infrastructure since
subsections already support arbitrary bytes, and avoids introducing
Unicode normalization.

Also teach the help subsystem about the new syntax so that "git help
-a" properly lists subsection aliases and the autocorrect feature can
suggest them. Use utf8_strwidth() instead of strlen() for column
alignment so that non-ASCII alias names display correctly.

Suggested-by: Jeff King <peff@peff.net>
Signed-off-by: Jonatan Holmgren <jonatan@jontes.page>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 11 insertions, 3 deletions

diff --git a/help.c b/help.c
index a781ebb98d..82fb2eaa3f 100644
--- a/help.c
+++ b/help.c
@@ -21,6 +21,7 @@
 #include "fsmonitor-ipc.h"
 #include "repository.h"
 #include "alias.h"
+#include "utf8.h"
 
 #ifndef NO_CURL
 #include "git-curl-compat.h" /* For LIBCURL_VERSION only */
@@ -108,7 +109,7 @@ static void print_command_list(const struct cmdname_help *cmds,
 
 	for (i = 0; cmds[i].name; i++) {
 		if (cmds[i].category & mask) {
-			size_t len = strlen(cmds[i].name);
+			size_t len = utf8_strwidth(cmds[i].name);
 			printf("   %s   ", cmds[i].name);
 			if (longest > len)
 				mput_char(' ', longest - len);
@@ -493,7 +494,7 @@ static void list_all_cmds_help_aliases(int longest)
 	string_list_sort(&alias_list);
 
 	for (i = 0; i < alias_list.nr; i++) {
-		size_t len = strlen(alias_list.items[i].string);
+		size_t len = utf8_strwidth(alias_list.items[i].string);
 		if (longest < len)
 			longest = len;
 	}
@@ -592,8 +593,15 @@ static int git_unknown_cmd_config(const char *var, const char *value,
 	/* Also use aliases for command lookup */
 	if (!parse_config_key(var, "alias", &subsection, &subsection_len,
 			      &key)) {
-		if (!subsection)
+		if (subsection) {
+			/* [alias "name"] command = value */
+			if (!strcmp(key, "command"))
+				add_cmdname(&cfg->aliases, subsection,
+					    subsection_len);
+		} else {
+			/* alias.name = value */
 			add_cmdname(&cfg->aliases, key, strlen(key));
+		}
 	}
 
 	return 0;