Factorize integer argument parsing

Add util functions for integer parsing (with tests), and factorize
integer argument parsing to avoid code duplication.

app/src/util/str_util.h

@@ -1,6 +1,7 @@
 #ifndef STRUTIL_H
 #define STRUTIL_H
 
+#include <stdbool.h>
 #include <stddef.h>
 
 #include "config.h"
@@ -25,6 +26,18 @@ xstrjoin(char *dst, const char *const tokens[], char sep, size_t n);
 char *
 strquote(const char *src);
 
+// parse s as an integer into value
+// returns true if the conversion succeeded, false otherwise
+bool
+parse_integer(const char *s, long *out);
+
+// parse s as an integer into value
+// like parse_integer(), but accept 'k'/'K' (x1000) and 'm'/'M' (x1000000) as
+// suffix
+// returns true if the conversion succeeded, false otherwise
+bool
+parse_integer_with_suffix(const char *s, long *out);
+
 // return the index to truncate a UTF-8 string at a valid position
 size_t
 utf8_truncation_index(const char *utf8, size_t max_len);