t6301: new tests of for-each-ref error handling

Add tests that for-each-ref correctly reports broken loose reference
files and references that point at missing objects. In fact, two of
these tests fail, because (1) NULL_SHA1 is not recognized as an
invalid reference value, and (2) for-each-ref doesn't respect
REF_ISBROKEN. Fixes to come.

Note that when for-each-ref is run with a --format option that doesn't
require the object to be looked up, then we should still notice if a
loose reference file is corrupt or contains NULL_SHA1, but we don't
notice if it points at a missing object because we don't do an object
lookup. This is OK.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t6301-for-each-ref-errors.sh

@@ -0,0 +1,56 @@
+#!/bin/sh
+
+test_description='for-each-ref errors for broken refs'
+
+. ./test-lib.sh
+
+ZEROS=$_z40
+MISSING=abababababababababababababababababababab
+
+test_expect_success setup '
+	git commit --allow-empty -m "Initial" &&
+	git tag testtag &&
+	git for-each-ref >full-list &&
+	git for-each-ref --format="%(objectname) %(refname)" >brief-list
+'
+
+test_expect_failure 'Broken refs are reported correctly' '
+	r=refs/heads/bogus &&
+	: >.git/$r &&
+	test_when_finished "rm -f .git/$r" &&
+	echo "warning: ignoring broken ref $r" >broken-err &&
+	git for-each-ref >out 2>err &&
+	test_cmp full-list out &&
+	test_cmp broken-err err
+'
+
+test_expect_failure 'NULL_SHA1 refs are reported correctly' '
+	r=refs/heads/zeros &&
+	echo $ZEROS >.git/$r &&
+	test_when_finished "rm -f .git/$r" &&
+	echo "warning: ignoring broken ref $r" >zeros-err &&
+	git for-each-ref >out 2>err &&
+	test_cmp full-list out &&
+	test_cmp zeros-err err &&
+	git for-each-ref --format="%(objectname) %(refname)" >brief-out 2>brief-err &&
+	test_cmp brief-list brief-out &&
+	test_cmp zeros-err brief-err
+'
+
+test_expect_success 'Missing objects are reported correctly' '
+	r=refs/heads/missing &&
+	echo $MISSING >.git/$r &&
+	test_when_finished "rm -f .git/$r" &&
+	echo "fatal: missing object $MISSING for $r" >missing-err &&
+	test_must_fail git for-each-ref 2>err &&
+	test_cmp missing-err err &&
+	(
+		cat brief-list &&
+		echo "$MISSING $r"
+	) | sort -k 2 >missing-brief-expected &&
+	git for-each-ref --format="%(objectname) %(refname)" >brief-out 2>brief-err &&
+	test_cmp missing-brief-expected brief-out &&
+	test_must_be_empty brief-err
+'
+
+test_done