Re: [PATCH v8] checkout: extend --track with a "fetch" mode to refresh start-point
- From
Junio C Hamano <gitster@pobox.com>
- Date
- May 12, 2026, 00:32 UTC
- Message-ID
- <xmqqh5odqxh2.fsf@gitster.g>
- In-Reply-To
- <pull.2281.v8.git.git.1778507225500.gitgitgadget@gmail.com>
"Harald Nordgren via GitGitGadget" <gitgitgadget@gmail.com> writes:
Show 21 quoted lines
> diff --git a/Documentation/git-checkout.adoc b/Documentation/git-checkout.adoc > index 43ccf47cf6..28f17f427e 100644 > --- a/Documentation/git-checkout.adoc > +++ b/Documentation/git-checkout.adoc > @@ -158,11 +158,22 @@ of it"). > resets _<branch>_ to the start point instead of failing. > > `-t`:: > -`--track[=(direct|inherit)]`:: > +`--track[=(direct|inherit|fetch)[,...]]`:: > When creating a new branch, set up "upstream" configuration. See > `--track` in linkgit:git-branch[1] for details. As a convenience, > --track without -b implies branch creation. > + > +The argument is a comma-separated list. `direct` (the default) and > +`inherit` select the tracking mode and are mutually exclusive. Adding > +`fetch` requests that the remote be fetched before _<start-point>_ is > +resolved, so the new branch starts from a fresh tip: when > +_<start-point>_ is in _<remote>/<branch>_ form, only that branch is > +updated; when _<start-point>_ is a bare remote name (e.g. `origin`), > +only the remote's default branch is updated.
The latter is because "checkout -t -b new remote/origin" makes "new" track "remote/origin/HEAD", which makes sense. And of course this fetch can fail.
Show 28 quoted lines
> +static int resolve_fetch_target(const char *arg, char **remote_out,
> + char **src_ref_out)
> +{
> + const char *slash;
> + char *remote_name;
> + struct remote *remote;
> + struct refspec_item query = { 0 };
> + struct strbuf dst = STRBUF_INIT;
> + const char *rest;
> +
> + *remote_out = NULL;
> + *src_ref_out = NULL;
> +
> + if (!arg || !*arg)
> + return -1;
> +
> + slash = strchr(arg, '/');
> + if (slash == arg)
> + return -1;
> + remote_name = slash ? xstrndup(arg, slash - arg) : xstrdup(arg);
> +
> + remote = remote_get(remote_name);
> + if (!remote || !remote_is_configured(remote, 1)) {
> + free(remote_name);
> + return -1;
> + }
> +
> + rest = (slash && slash[1]) ? slash + 1 : NULL;There is no slash when asking for "origin", and the control goes into the "if (!rest)" block.
Show 18 quoted lines
> + if (!rest) {
> + struct object_id oid;
> + const char *head_target;
> + const char *short_target;
> +
> + strbuf_addf(&dst, "refs/remotes/%s/HEAD", remote_name);
> + head_target = refs_resolve_ref_unsafe(get_main_ref_store(the_repository),
> + dst.buf,
> + RESOLVE_REF_READING |
> + RESOLVE_REF_NO_RECURSE,
> + &oid, NULL);
> + strbuf_reset(&dst);
> + if (head_target &&
> + skip_prefix(head_target, "refs/remotes/", &short_target) &&
> + skip_prefix(short_target, remote_name, &short_target) &&
> + *short_target == '/')
> + rest = short_target + 1;
> + }If refs/remotes/origin/HEAD points at refs/remotes/origin/main, rest gets "main". Otherwise (i.e. unexpected contents in HEAD or lacking HEAD), rest remains NULL. And then we have the "if (rest)" block.
Show 15 quoted lines
> + if (rest) {
> + strbuf_addf(&dst, "refs/remotes/%s/%s", remote_name, rest);
> + query.dst = dst.buf;
> + if (!remote_find_tracking(remote, &query) && query.src) {
> + *src_ref_out = xstrdup(query.src);
> + free(query.src);
> + } else {
> + *src_ref_out = xstrdup(rest);
> + }
> + }
> +
> + strbuf_release(&dst);
> + *remote_out = remote_name;
> + return 0;
> +}It is not a new problem but I do not remember how we explicitly forbid "hierarchical" remote names. refs/remotes/a/b/c might be their branch "b/c" at remote we call "a", or branch "c" at remote "a/b". Unless we forbid slashes in remote names, the "there is no slash so we got only the name of the remote to mean its HEAD" logic would not work well, so we may want to double check.
Show 22 quoted lines
> +static void fetch_remote_for_start_point(const char *arg)
> +{
> + char *remote_name = NULL;
> + char *src_ref = NULL;
> + struct child_process cmd = CHILD_PROCESS_INIT;
> + struct strbuf dst_ref = STRBUF_INIT;
> + int have_existing_ref = 0;
> +
> + if (resolve_fetch_target(arg, &remote_name, &src_ref))
> + return;
> +
> + {
> + struct object_id oid;
> +
> + if (strchr(arg, '/'))
> + strbuf_addf(&dst_ref, "refs/remotes/%s", arg);
> + else
> + strbuf_addf(&dst_ref, "refs/remotes/%s/HEAD", arg);
> + if (!refs_read_ref(get_main_ref_store(the_repository),
> + dst_ref.buf, &oid))
> + have_existing_ref = 1;
> + }I do not quite see the point of this extra block. Can we do without it (and move the def of oid up near the beginning of the function, of course)?
Even better, as resolve_fetch_target() already looks at "arg" and poked at the remote-tracking ref hierarchy, wouldn't it make more sense to make that helper function responsible for finding out if there already is a usable, albeit potentially stale, ref?
Show 17 quoted lines
> + strvec_pushl(&cmd.args, "fetch", remote_name, NULL);
> + if (src_ref)
> + strvec_push(&cmd.args, src_ref);
> + cmd.git_cmd = 1;
> + if (run_command(&cmd)) {
> + if (have_existing_ref)
> + warning(_("failed to fetch start-point '%s'; "
> + "using existing '%s'"),
> + arg, dst_ref.buf);
> + else
> + die(_("failed to fetch start-point '%s'"), arg);
> + }
> +
> + free(remote_name);
> + free(src_ref);
> + strbuf_release(&dst_ref);
> +}Show 7 quoted lines
> @@ -1244,7 +1398,6 @@ static int git_checkout_config(const char *var, const char *value, > opts->dwim_new_local_branch = git_config_bool(var, value); > return 0; > } > - > if (starts_with(var, "submodule.")) > return git_default_submodule_config(var, value, NULL);
Unrelated patch noise?