Merge branch 'sg/name-rev-cutoff-underflow-fix'

Integer arithmetic fix.

* sg/name-rev-cutoff-underflow-fix:
  name-rev: avoid cutoff timestamp underflow

builtin/name-rev.c

@@ -9,7 +9,11 @@
 #include "sha1-lookup.h"
 #include "commit-slab.h"
 
-#define CUTOFF_DATE_SLOP 86400 /* one day */
+/*
+ * One day.  See the 'name a rev shortly after epoch' test in t6120 when
+ * changing this value
+ */
+#define CUTOFF_DATE_SLOP 86400
 
 typedef struct rev_name {
 	const char *tip_name;
@@ -481,8 +485,13 @@ int cmd_name_rev(int argc, const char **argv, const char *prefix)
 		add_object_array(object, *argv, &revs);
 	}
 
-	if (cutoff)
-		cutoff = cutoff - CUTOFF_DATE_SLOP;
+	if (cutoff) {
+		/* check for undeflow */
+		if (cutoff > TIME_MIN + CUTOFF_DATE_SLOP)
+			cutoff = cutoff - CUTOFF_DATE_SLOP;
+		else
+			cutoff = TIME_MIN;
+	}
 	for_each_ref(name_ref, &data);
 
 	if (transform_stdin) {

git-compat-util.h

@@ -344,6 +344,7 @@ typedef uintmax_t timestamp_t;
 #define PRItime PRIuMAX
 #define parse_timestamp strtoumax
 #define TIME_MAX UINTMAX_MAX
+#define TIME_MIN 0
 
 #ifndef PATH_SEP
 #define PATH_SEP ':'

t/t6120-describe.sh

@@ -424,4 +424,19 @@ test_expect_success 'describe complains about missing object' '
 	test_must_fail git describe $ZERO_OID
 '
 
+test_expect_success 'name-rev a rev shortly after epoch' '
+	test_when_finished "git checkout master" &&
+
+	git checkout --orphan no-timestamp-underflow &&
+	# Any date closer to epoch than the CUTOFF_DATE_SLOP constant
+	# in builtin/name-rev.c.
+	GIT_COMMITTER_DATE="@1234 +0000" \
+	git commit -m "committer date shortly after epoch" &&
+	old_commit_oid=$(git rev-parse HEAD) &&
+
+	echo "$old_commit_oid no-timestamp-underflow" >expect &&
+	git name-rev $old_commit_oid >actual &&
+	test_cmp expect actual
+'
+
 test_done