Merge branch 'maint'

* maint:
  gitweb: use decode_utf8 directly
  posix compatibility for t4200
  Document 'opendiff' value in config.txt and git-mergetool.txt
  Allow PERL_PATH="/usr/bin/env perl"
  Make xstrndup common
  diff.c: fix "size cache" handling.
  http-fetch: Disable use of curl multi support for libcurl < 7.16.

git-compat-util.h

@@ -197,6 +197,19 @@ static inline void *xmalloc(size_t size)
 	return ret;
 }
 
+static inline char *xstrndup(const char *str, size_t len)
+{
+	char *p;
+
+	p = memchr(str, '\0', len);
+	if (p)
+		len = p - str;
+	p = xmalloc(len + 1);
+	memcpy(p, str, len);
+	p[len] = '\0';
+	return p;
+}
+
 static inline void *xrealloc(void *ptr, size_t size)
 {
 	void *ret = realloc(ptr, size);