Merge branch 'jk/utf-8-can-be-spelled-differently' into maint

Some platforms and users spell UTF-8 differently; retry with the
most official "UTF-8" when the system does not understand the
user-supplied encoding name that are the common alternative
spellings of UTF-8.

* jk/utf-8-can-be-spelled-differently:
  utf8: accept alternate spellings of UTF-8

Author: gitster

utf8.c

@@ -507,9 +507,25 @@ char *reencode_string(const char *in, const char *out_encoding, const char *in_e
 
 	if (!in_encoding)
 		return NULL;
+
 	conv = iconv_open(out_encoding, in_encoding);
-	if (conv == (iconv_t) -1)
-		return NULL;
+	if (conv == (iconv_t) -1) {
+		/*
+		 * Some platforms do not have the variously spelled variants of
+		 * UTF-8, so let's fall back to trying the most official
+		 * spelling. We do so only as a fallback in case the platform
+		 * does understand the user's spelling, but not our official
+		 * one.
+		 */
+		if (is_encoding_utf8(in_encoding))
+			in_encoding = "UTF-8";
+		if (is_encoding_utf8(out_encoding))
+			out_encoding = "UTF-8";
+		conv = iconv_open(out_encoding, in_encoding);
+		if (conv == (iconv_t) -1)
+			return NULL;
+	}
+
 	out = reencode_string_iconv(in, strlen(in), conv);
 	iconv_close(conv);
 	return out;