set errno=0 before strtoX calls

To detect conversion failure after calls to functions like `strtod`, one
can check `errno == ERANGE`. These functions are not guaranteed to set
`errno` to `0` on successful conversion, however. Manual manipulation of
`errno` can likely be avoided by checking that the output pointer
differs from the input pointer, but that's not how other locations, such
as parse.c:139, handle this issue; they set errno to 0 prior to
executing the function.

For every place I could find a strtoX function with an ERANGE check
following it, set `errno = 0;` prior to executing the conversion
function.

Signed-off-by: Kyle Lippincott <spectral@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/get-tar-commit-id.c

@@ -35,6 +35,7 @@ int cmd_get_tar_commit_id(int argc, const char **argv UNUSED, const char *prefix
 	if (header->typeflag[0] != TYPEFLAG_GLOBAL_HEADER)
 		return 1;
 
+	errno = 0;
 	len = strtol(content, &end, 10);
 	if (errno == ERANGE || end == content || len < 0)
 		return 1;

ref-filter.c

@@ -1628,6 +1628,7 @@ static void grab_date(const char *buf, struct atom_value *v, const char *atomnam
 	timestamp = parse_timestamp(eoemail + 2, &zone, 10);
 	if (timestamp == TIME_MAX)
 		goto bad;
+	errno = 0;
 	tz = strtol(zone, NULL, 10);
 	if ((tz == LONG_MIN || tz == LONG_MAX) && errno == ERANGE)
 		goto bad;

t/helper/test-json-writer.c

@@ -415,6 +415,7 @@ static void get_i(struct line *line, intmax_t *s_in)
 
 	get_s(line, &s);
 
+	errno = 0;
 	*s_in = strtol(s, &endptr, 10);
 	if (*endptr || errno == ERANGE)
 		die("line[%d]: invalid integer value", line->nr);
@@ -427,6 +428,7 @@ static void get_d(struct line *line, double *s_in)
 
 	get_s(line, &s);
 
+	errno = 0;
 	*s_in = strtod(s, &endptr);
 	if (*endptr || errno == ERANGE)
 		die("line[%d]: invalid float value", line->nr);

t/helper/test-trace2.c

@@ -26,6 +26,7 @@ static int get_i(int *p_value, const char *data)
 	if (!data || !*data)
 		return MyError;
 
+	errno = 0;
 	*p_value = strtol(data, &endptr, 10);
 	if (*endptr || errno == ERANGE)
 		return MyError;