wildmatch: advance faster in <asterisk> + <literal> patterns

Normally when we match "*X" on "abcX", we call dowild("X", "abcX"),
dowild("X", "bcX"), dowild("X", "cX") and dowild("X", "X"). Only the
last call may have a chance of matching. By skipping the text before
"X", we can eliminate the first three useless calls.

compat, '*/*/*' on linux-2.6.git file list 2000 times, before:
wildmatch 7s 985049us
fnmatch   2s 735541us or 34.26% faster

and after:
wildmatch 4s 492549us
fnmatch   0s 888263us or 19.77% slower

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3070-wildmatch.sh

@@ -207,6 +207,11 @@ match 0 x foo '*/*/*'
 match 0 x foo/bar '*/*/*'
 match 1 x foo/bba/arr '*/*/*'
 match 0 x foo/bb/aa/rr '*/*/*'
+match 1 x foo/bb/aa/rr '**/**/**'
+match 1 x abcXdefXghi '*X*i'
+match 0 x ab/cXd/efXg/hi '*X*i'
+match 1 x ab/cXd/efXg/hi '*/*X*/*/*i'
+match 1 x ab/cXd/efXg/hi '**/*X*/**/*i'
 
 pathmatch 1 foo foo
 pathmatch 0 foo fo
@@ -226,5 +231,8 @@ pathmatch 0 foo '*/*/*'
 pathmatch 0 foo/bar '*/*/*'
 pathmatch 1 foo/bba/arr '*/*/*'
 pathmatch 1 foo/bb/aa/rr '*/*/*'
+pathmatch 1 abcXdefXghi '*X*i'
+pathmatch 1 ab/cXd/efXg/hi '*/*X*/*/*i'
+pathmatch 1 ab/cXd/efXg/hi '*Xg*i'
 
 test_done

wildmatch.c

@@ -133,6 +133,29 @@ static int dowild(const uchar *p, const uchar *text, unsigned int flags)
 			while (1) {
 				if (t_ch == '\0')
 					break;
+				/*
+				 * Try to advance faster when an asterisk is
+				 * followed by a literal. We know in this case
+				 * that the the string before the literal
+				 * must belong to "*".
+				 * If match_slash is false, do not look past
+				 * the first slash as it cannot belong to '*'.
+				 */
+				if (!is_glob_special(*p)) {
+					p_ch = *p;
+					if ((flags & WM_CASEFOLD) && ISUPPER(p_ch))
+						p_ch = tolower(p_ch);
+					while ((t_ch = *text) != '\0' &&
+					       (match_slash || t_ch != '/')) {
+						if ((flags & WM_CASEFOLD) && ISUPPER(t_ch))
+							t_ch = tolower(t_ch);
+						if (t_ch == p_ch)
+							break;
+						text++;
+					}
+					if (t_ch != p_ch)
+						return WM_NOMATCH;
+				}
 				if ((matched = dowild(p, text, flags)) != WM_NOMATCH) {
 					if (!match_slash || matched != WM_ABORT_TO_STARSTAR)
 						return matched;