git/builtin-symbolic-ref.c
Jeff King afe5d3d516 symbolic ref: refuse non-ref targets in HEAD
When calling "git symbolic-ref" it is easy to forget that
the target must be a fully qualified ref. E.g., you might
accidentally do:

  $ git symbolic-ref HEAD master

Unfortunately, this is very difficult to recover from,
because the bogus contents of HEAD make git believe we are
no longer in a git repository (as is_git_dir explicitly
checks for "^refs/heads/" in the HEAD target). So
immediately trying to fix the situation doesn't work:

  $ git symbolic-ref HEAD refs/heads/master
  fatal: Not a git repository

and one is left editing the .git/HEAD file manually.

Furthermore, one might be tempted to use symbolic-ref to set
up a detached HEAD:

  $ git symbolic-ref HEAD `git rev-parse HEAD`

which sets up an even more bogus HEAD:

  $ cat .git/HEAD
  ref: 1a9ace4f2ad4176148e61b5a85cd63d5604aac6d

This patch introduces a small safety valve to prevent the
specific case of anything not starting with refs/heads/ to
go into HEAD. The scope of the safety valve is intentionally
very limited, to make sure that we are not preventing any
behavior that would otherwise be valid (like pointing a
different symref than HEAD outside of refs/heads/).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2009-01-29 01:00:48 -08:00

57 lines
1.3 KiB
C

#include "builtin.h"
#include "cache.h"
#include "refs.h"
#include "parse-options.h"
static const char * const git_symbolic_ref_usage[] = {
"git symbolic-ref [options] name [ref]",
NULL
};
static void check_symref(const char *HEAD, int quiet)
{
unsigned char sha1[20];
int flag;
const char *refs_heads_master = resolve_ref(HEAD, sha1, 0, &flag);
if (!refs_heads_master)
die("No such ref: %s", HEAD);
else if (!(flag & REF_ISSYMREF)) {
if (!quiet)
die("ref %s is not a symbolic ref", HEAD);
else
exit(1);
}
puts(refs_heads_master);
}
int cmd_symbolic_ref(int argc, const char **argv, const char *prefix)
{
int quiet = 0;
const char *msg = NULL;
struct option options[] = {
OPT__QUIET(&quiet),
OPT_STRING('m', NULL, &msg, "reason", "reason of the update"),
OPT_END(),
};
git_config(git_default_config, NULL);
argc = parse_options(argc, argv, options, git_symbolic_ref_usage, 0);
if (msg &&!*msg)
die("Refusing to perform update with empty message");
switch (argc) {
case 1:
check_symref(argv[0], quiet);
break;
case 2:
if (!strcmp(argv[0], "HEAD") &&
prefixcmp(argv[1], "refs/heads/"))
die("Refusing to point HEAD outside of refs/heads/");
create_symref(argv[0], argv[1], msg);
break;
default:
usage_with_options(git_symbolic_ref_usage, options);
}
return 0;
}