[PATCH] [RFC] shell: allow overriding built-in commands

From: Ayman Bagabas via GitGitGadget <gitgitgadget@gmail.com>
Date: Mar 22, 2025, 10:01 UTC
Message-ID: <pull.1930.git.git.1742637713157.gitgitgadget@gmail.com>

From: Ayman Bagabas <ayman.bagabas@gmail.com>

This patch allows overriding built-in commands by placing a script with the same name under git-shell-commands directory.

This is useful for users who want to extend the built-in commands without replacing the original command binary. For instance, a user wanting to allow only a subset of users to run the git-receive-pack can override the command with a script that checks the user and calls the original command if the user is allowed.

CC: Junio C Hamano <gitster@pobox.com>, Jeff King <peff@peff.net>
CC: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Ayman Bagabas <ayman.bagabas@gmail.com>
---
    [RFC] shell: allow overriding built-in commands

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1930%2Faymanbagabas%2Fshell-override-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1930/aymanbagabas/shell-override-v1
Pull-Request: https://github.com/git/git/pull/1930

 shell.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/shell.c b/shell.c
index 76333c80686..3a6d2e8a044 100644
--- a/shell.c
+++ b/shell.c
@@ -194,9 +194,11 @@ int cmd_main(int argc, const char **argv)
 		/* Accept "git foo" as if the caller said "git-foo". */
 		prog[3] = '-';
 
+	cd_to_homedir();
 	for (cmd = cmd_list ; cmd->name ; cmd++) {
 		int len = strlen(cmd->name);
 		char *arg;
+		char *full_cmd;
 		if (strncmp(cmd->name, prog, len))
 			continue;
 		arg = NULL;
@@ -210,10 +212,16 @@ int cmd_main(int argc, const char **argv)
 		default:
 			continue;
 		}
-		return cmd->exec(cmd->name, arg);
+		/* Allow overriding built-in commands */
+		full_cmd = make_cmd(cmd->name);
+		if (!access(full_cmd, F_OK)) {
+			const char *argv[3] = { cmd->name, arg, NULL };
+			return execv(full_cmd, (char *const *) argv);
+		} else {
+			return cmd->exec(cmd->name, arg);
+		}
 	}
 
-	cd_to_homedir();
 	count = split_cmdline(prog, &user_argv);
 	if (count >= 0) {
 		if (is_valid_cmd_name(user_argv[0])) {

base-commit: 683c54c999c301c2cd6f715c411407c413b1d84e

-- 
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