Add case insensitivity support when using git ls-files

When mydir/filea.txt is added, mydir/ is renamed to MyDir/, and
MyDir/fileb.txt is added, running git ls-files mydir only shows
mydir/filea.txt. Running git ls-files MyDir shows MyDir/fileb.txt.
Running git ls-files mYdIR shows nothing.

With this patch running git ls-files for mydir, MyDir, and mYdIR shows
mydir/filea.txt and MyDir/fileb.txt.

Wildcards are not handled case insensitively in this patch. Example:
MyDir/aBc/file.txt is added. git ls-files MyDir/a* works fine, but git
ls-files mydir/a* does not.
Signed-off-by: NJoshua Jensen <jjensen@workspacewhiz.com>
Signed-off-by: NJohannes Sixt <j6t@kdbg.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

dir.c

@@ -107,16 +107,30 @@ static int match_one(const char *match, const char *name, int namelen)
 	if (!*match)
 		return MATCHED_RECURSIVELY;
 
-	for (;;) {
-		unsigned char c1 = *match;
-		unsigned char c2 = *name;
-		if (c1 == '\0' || is_glob_special(c1))
-			break;
-		if (c1 != c2)
-			return 0;
-		match++;
-		name++;
-		namelen--;
+	if (ignore_case) {
+		for (;;) {
+			unsigned char c1 = tolower(*match);
+			unsigned char c2 = tolower(*name);
+			if (c1 == '\0' || is_glob_special(c1))
+				break;
+			if (c1 != c2)
+				return 0;
+			match++;
+			name++;
+			namelen--;
+		}
+	} else {
+		for (;;) {
+			unsigned char c1 = *match;
+			unsigned char c2 = *name;
+			if (c1 == '\0' || is_glob_special(c1))
+				break;
+			if (c1 != c2)
+				return 0;
+			match++;
+			name++;
+			namelen--;
+		}
 	}
 
 
@@ -125,8 +139,8 @@ static int match_one(const char *match, const char *name, int namelen)
 	 * we need to match by fnmatch
 	 */
 	matchlen = strlen(match);
-	if (strncmp(match, name, matchlen))
-		return !fnmatch(match, name, 0) ? MATCHED_FNMATCH : 0;
+	if (strncmp_icase(match, name, matchlen))
+		return !fnmatch_icase(match, name, 0) ? MATCHED_FNMATCH : 0;
 
 	if (namelen == matchlen)
 		return MATCHED_EXACTLY;