git-compat-util: add strtoul_ul() with error handling

We already have strtoul_ui() and similar functions that provide proper
error handling using strtoul from the standard library. However,
there isn't currently a variant that returns an unsigned long.
This commit introduces strtoul_ul() to address this gap, enabling the
return of an unsigned long with proper error handling.

Signed-off-by: Junio C Hamano <[email protected]>

Author: peijianju

git-compat-util.h

@@ -1353,6 +1353,26 @@ static inline int strtoul_ui(char const *s, int base, unsigned int *result)
 	return 0;
 }
 
+/*
+ * Convert a string to an unsigned long using the standard library's strtoul,
+ * with additional error handling to ensure robustness.
+ */
+static inline int strtoul_ul(char const *s, int base, unsigned long *result)
+{
+	unsigned long ul;
+	char *p;
+
+	errno = 0;
+	/* negative values would be accepted by strtoul */
+	if (strchr(s, '-'))
+		return -1;
+	ul = strtoul(s, &p, base);
+	if (errno || *p || p == s )
+		return -1;
+	*result = ul;
+	return 0;
+}
+
 static inline int strtol_i(char const *s, int base, int *result)
 {
 	long ul;