log: diagnose empty HEAD more clearly

If you init or clone an empty repository, the initial
message from running "git log" is not very friendly:

$ git init
Initialized empty Git repository in /home/peff/foo/.git/
$ git log
fatal: bad default revision 'HEAD'

Let's detect this situation and write a more friendly
message:

$ git log
fatal: your current branch 'master' does not have any commits yet

We also detect the case that 'HEAD' points to a broken ref;
this should be even less common, but is easy to see. Note
that we do not diagnose all possible cases. We rely on
resolve_ref, which means we do not get information about
complex cases. E.g., "--default master" would use dwim_ref
to find "refs/heads/master", but we notice only that
"master" does not exist. Similarly, a complex sha1
expression like "--default HEAD^2" will not resolve as a
ref.

But that's OK. We fall back to a generic error message in
those cases, and they are unlikely to be used anyway.
Catching an empty or broken "HEAD" improves the common case,
and the other cases are not regressed.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/revision.c b/revision.c
index 7ddbaa083e9e59d3db270b96b47a20e6c99bdaa3..734494abe6af2288e2f0bf6ad31eb5b74db9ea9c 100644 (file)
--- a/revision.c
+++ b/revision.c
@@ -2170,6 +2170,21 @@ static int handle_revision_pseudo_opt(const char *submodule,
        return 1;
 }
 
        return 1;
 }
 

+static void NORETURN diagnose_missing_default(const char *def)
+{
+       unsigned char sha1[20];
+       int flags;
+       const char *refname;
+
+       refname = resolve_ref_unsafe(def, 0, sha1, &flags);
+       if (!refname || !(flags & REF_ISSYMREF) || (flags & REF_ISBROKEN))
+               die(_("your current branch appears to be broken"));
+
+       skip_prefix(refname, "refs/heads/", &refname);
+       die(_("your current branch '%s' does not have any commits yet"),
+           refname);
+}
+

 /*
  * Parse revision information, filling in the "rev_info" structure,
  * and removing the used arguments from the argument list.
 /*
  * Parse revision information, filling in the "rev_info" structure,
  * and removing the used arguments from the argument list.


@@ -2299,7 +2314,7 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
                struct object *object;
                struct object_context oc;
                if (get_sha1_with_context(revs->def, 0, sha1, &oc))
                struct object *object;
                struct object_context oc;
                if (get_sha1_with_context(revs->def, 0, sha1, &oc))

-                       die("bad default revision '%s'", revs->def);
+                       diagnose_missing_default(revs->def);

                object = get_reference(revs, revs->def, sha1, 0);
                add_pending_object_with_mode(revs, object, revs->def, oc.mode);
        }
                object = get_reference(revs, revs->def, sha1, 0);
                add_pending_object_with_mode(revs, object, revs->def, oc.mode);
        }

diff --git a/t/t4202-log.sh b/t/t4202-log.sh
index 1b2e981a0011d520d1a7d8bb8d0a5fd7892bacc4..19277dd3618019a97ef0631cc4a808f5e5bcc653 100755 (executable)
--- a/t/t4202-log.sh
+++ b/t/t4202-log.sh
@@ -871,4 +871,18 @@ test_expect_success 'log --graph --no-walk is forbidden' '
        test_must_fail git log --graph --no-walk
 '
 
        test_must_fail git log --graph --no-walk
 '
 

+test_expect_success 'log diagnoses bogus HEAD' '
+       git init empty &&
+       test_must_fail git -C empty log 2>stderr &&
+       test_i18ngrep does.not.have.any.commits stderr &&
+       echo 1234abcd >empty/.git/refs/heads/master &&
+       test_must_fail git -C empty log 2>stderr &&
+       test_i18ngrep broken stderr &&
+       echo "ref: refs/heads/invalid.lock" >empty/.git/HEAD &&
+       test_must_fail git -C empty log 2>stderr &&
+       test_i18ngrep broken stderr &&
+       test_must_fail git -C empty log --default totally-bogus 2>stderr &&
+       test_i18ngrep broken stderr
+'
+

 test_done
 test_done