Re: [PATCH] git-gui: give more advice when detaching HEAD

From

Junio C Hamano <gitster@pobox.com>

Date

Feb 17, 2011, 23:13 UTC

Message-ID

<7vvd0i8dbc.fsf@alter.siamese.dyndns.org>

In-Reply-To

<20110212082108.GA19656@sigill.intra.peff.net>

Jeff King <peff@peff.net> writes:

> Want to do a proof-of-concept patch? Then we can get some real timings.

This was about 

> >   2. When leaving the detached state, notice that we have commits not
> >      contained in any other ref and pop up an "are you sure you want to
> >      lose these commits" dialog, with an option to create a branch. This
> >      is something we considered and rejected for the CLI, but I wonder
> >      if it makes more sense for git-gui.

 builtin/checkout.c |   66 +++++++++++++++++++++++++++++++++++++++++++++++----
 1 files changed, 60 insertions(+), 6 deletions(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index cd7f56e..1f5376f 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -503,6 +503,17 @@ static void detach_advice(const char *old_path, const char *new_name)
 	fprintf(stderr, fmt, new_name);
 }
 
+static void suggest_reattach(struct commit *commit)
+{
+	const char fmt[] =
+	"Note: you are about to abandon commit %1$s\n\n"
+	"None of your branches nor tags refer to this commit. If you want to\n"
+	"keep this commit, you can do so by creating a new branch. Example:\n\n"
+	" git branch new_branch_name %1$s\n\n";
+
+	fprintf(stderr, fmt, sha1_to_hex(commit->object.sha1));
+}
+
 static void update_refs_for_switch(struct checkout_opts *opts,
 				   struct branch_info *old,
 				   struct branch_info *new)
@@ -578,6 +589,54 @@ static void update_refs_for_switch(struct checkout_opts *opts,
 		report_tracking(new);
 }
 
+struct rev_list_args {
+	int argc;
+	int alloc;
+	const char **argv;
+};
+
+static void add_one_rev_list_arg(struct rev_list_args *args, const char *s)
+{
+	ALLOC_GROW(args->argv, args->argc + 1, args->alloc);
+	args->argv[args->argc++] = s;
+}
+
+static int add_one_ref_to_rev_list_arg(const char *refname,
+				       const unsigned char *sha1,
+				       int flags,
+				       void *cb_data)
+{
+	add_one_rev_list_arg(cb_data, refname);
+	return 0;
+}
+
+/*
+ * We are about to leave commit that was at the tip of a detached
+ * HEAD.  If it is not reachable from any ref, this is the last chance
+ * for the user to do so without resorting to reflog.
+ */
+static void orphaned_commit_warning(struct commit *commit)
+{
+	struct rev_list_args args = { 0, 0, NULL };
+	struct rev_info revs;
+
+	add_one_rev_list_arg(&args, "(internal)");
+	add_one_rev_list_arg(&args, sha1_to_hex(commit->object.sha1));
+	add_one_rev_list_arg(&args, "--not");
+	for_each_ref(add_one_ref_to_rev_list_arg, &args);
+	add_one_rev_list_arg(&args, "--");
+	add_one_rev_list_arg(&args, NULL);
+
+	init_revisions(&revs, NULL);
+	if (setup_revisions(args.argc - 1, args.argv, &revs, NULL) != 1)
+		die("internal error: only -- alone should have been left");
+	if (prepare_revision_walk(&revs))
+		die("internal error in revision walk");
+	if (!(commit->object.flags & UNINTERESTING))
+		suggest_reattach(commit);
+	describe_detached_head("Previous HEAD position was", commit);
+}
+
 static int switch_branches(struct checkout_opts *opts, struct branch_info *new)
 {
 	int ret = 0;
@@ -605,13 +664,8 @@ static int switch_branches(struct checkout_opts *opts, struct branch_info *new)
 	if (ret)
 		return ret;
 
-	/*
-	 * If we were on a detached HEAD, but have now moved to
-	 * a new commit, we want to mention the old commit once more
-	 * to remind the user that it might be lost.
-	 */
 	if (!opts->quiet && !old.path && old.commit && new->commit != old.commit)
-		describe_detached_head("Previous HEAD position was", old.commit);
+		orphaned_commit_warning(old.commit);
 
 	update_refs_for_switch(opts, &old, new);