Re: [PATCH] log: diagnose empty HEAD more clearly

Jeff King [off-list ref] writes:

But if you are OK to eventually stop dying, I think this line of
reasoning is OK.

quoted

diff --git a/builtin/log.c b/builtin/log.c
index 4c4e6be..3b568a1 100644
--- a/builtin/log.c
+++ b/builtin/log.c

@@ -148,6 +148,9 @@ static void cmd_log_init_finish(int argc, const char **argv, const char *prefix,
 		rev->diffopt.output_format |= DIFF_FORMAT_NO_OUTPUT;
 	argc = setup_revisions(argc, argv, rev, opt);
 
+	if (!rev->pending.nr && !opt->def)
+		die("you do not have a commit yet on your branch");

Do we want to mention the name of the branch here? I guess it does not
really matter. Perhaps "the current branch" would be better than "your
branch", though. Maybe:

  fatal: you do not have any commits yet on the current branch

This message hopefully goes away in the long run, but we'll have it for
a while.

quoted

+static void default_to_head_if_exists(struct setup_revision_opt *opt)
+{
+	unsigned char unused[20];
+
+	if (resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, unused, NULL))
+		opt->def = "HEAD";
+}

This approach looks sane to me. Want to wrap it up with a commit
message and a test?

There is an unmerged attempt jc/log-missing-default-HEAD in my
"broken-out" repository https://github.com/gitster/git; I do agree
that we should spend more cycles after deciding to error out to
give a more detailed diagnosis, but I didn't have enough energy
to bring myself do that, so I've tentatively merged your version
instead of this one.