On Sat, 16 Feb 2008, Junio C Hamano wrote:
> Junio C Hamano <gitster@xxxxxxxxx> writes:
>
> > Perhaps making "git-checkout" to notice this and offer (or
> > suggest) fast-forwarding at that point may be safer and make
> > more sense. You cannot grow your local branch unless you check
> > them out, and your remote tracking will keep growing without the
> > auto-ff you are suggesting, so it is not like people will lose
> > anchoring point to compare between branches if we do not
> > auto-ff.
>
> So I did this.
>
> When you are switching to a branch that is marked to merge from
> somewhere else, e.g. when you have:
>
> [branch "next"]
> remote = upstream
> merge = refs/heads/next
> [remote "upstream"]
> url = ...
> fetch = refs/heads/*:refs/remotes/linus/*
>
> and you say "git checkout next", then after we switch the branch
> we check the upstream (in this case, refs/remotes/linus/next)
> and our branch, and:
>
> (1) if they match, nothing happens;
>
> (2) if you are ahead (i.e. the upstream is a strict ancestor
> of you), one line message tells you so;
>
> (3) otherwise, you are either behind or you and the upstream
> have forked. One line message will tell you which and
> then you will see a "log --pretty=oneline --left-right".
I like this idea a lot. I'd actually also like it for commit, although (1)
and (3a) obviously don't happen there. It would help to combat my tendency
to forget to push when I mean to.
Note that, in addition to "should I merge before starting to work now",
this also answers "if I turn off this computer, what can't I get at".
> We could enhance this with an option that tells the command to
> check if there is no local change, and automatically fast
> forward when you are truly behind. But I ripped out that change
> because I was unsure what the right way should be to allow users
> to control it (issues include that checkout should not become
> automatically interactive).
I suppose you could use a config option to enable it per-branch.
It would be really clever to make it happen if you do:
$ git checkout next
(fast-forward info)
$ git checkout
But that's probably a bit too clever.
> diff --git a/builtin-checkout.c b/builtin-checkout.c
> index 59a0ef4..9370ba0 100644
> --- a/builtin-checkout.c
> +++ b/builtin-checkout.c
> @@ -12,6 +12,7 @@
> #include "branch.h"
> #include "diff.h"
> #include "revision.h"
> +#include "remote.h"
>
> static const char * const checkout_usage[] = {
> "git checkout [options] <branch>",
> @@ -290,6 +291,139 @@ static int merge_working_tree(struct checkout_opts *opts,
> return 0;
> }
>
> +/*
> + * We really should allow cb_data... Yuck
> + */
> +static const char *branch_name;
> +static int branch_name_len;
> +static char *found_remote;
> +static char *found_merge;
> +static int read_branch_config(const char *var, const char *value)
> +{
...
I think you want branch_get(), which handles all the config file stuff up
to approximately here:
> + remote = remote_get(found_remote);
> + memset(&spec, 0, sizeof(spec));
> + spec.src = found_merge;
> + if (remote_find_tracking(remote, &spec))
> + goto cleanup;
> + *base = spec.dst;
> + return 1;
> +}
> +
> +static void adjust_to_tracking(struct branch_info *new, struct checkout_opts *opts)
> +{
> + /*
> + * We have switched to a new branch; is it building on
> + * top of another branch, and if so does that other branch
> + * have changes we do not have yet?
> + */
> + char *base;
> + unsigned char sha1[20];
> + struct commit *ours, *theirs;
> + const char *msgfmt;
> + char symmetric[84];
> + int show_log;
> +
> + if (!resolve_ref(new->path, sha1, 1, NULL))
> + return;
> + ours = lookup_commit(sha1);
> +
> + if (!find_build_base(new->path, &base))
> + return;
> +
> + sprintf(symmetric, "%s", sha1_to_hex(sha1));
> +
> + /*
> + * Ok, it is tracking base; is it ahead of us?
> + */
> + if (!resolve_ref(base, sha1, 1, NULL))
> + return;
> + theirs = lookup_commit(sha1);
> +
> + sprintf(symmetric + 40, "...%s", sha1_to_hex(sha1));
> +
> + if (!hashcmp(sha1, ours->object.sha1))
> + return; /* we are the same */
> +
> + show_log = 1;
> + if (in_merge_bases(theirs, &ours, 1)) {
> + msgfmt = "You are ahead of the tracked branch '%s'\n";
> + show_log = 0;
> + }
> + else if (in_merge_bases(ours, &theirs, 1))
> + msgfmt = "Your branch can be fast-forwarded to the tracked branch '%s'\n";
> + else
> + msgfmt = "Both your branch and the tracked branch '%s' have own changes, you would eventually need to merge\n";
> +
> + if (!prefixcmp(base, "refs/remotes/"))
> + base += strlen("refs/remotes/");
> + fprintf(stderr, msgfmt, base);
> +
> + if (show_log) {
> + const char *args[32];
> + int ac;
> +
> + ac = 0;
> + args[ac++] = "log";
> + args[ac++] = "--pretty=oneline";
> + args[ac++] = "--abbrev-commit";
> + args[ac++] = "--left-right";
> + args[ac++] = "--boundary";
> + args[ac++] = symmetric;
> + args[ac++] = "--";
> + args[ac] = NULL;
> +
> + run_command_v_opt(args, RUN_GIT_CMD);
We really should be able to do this in-process, although I'm not sure if
we really can. I don't think I've marked up the history in
builtin-checkout for anything else yet, anyway.
-Daniel
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