util._matcher: speed up regexp matching.
In 4babaa52badf, Benoit made a change that substantially slows matching
when a big .hgignore file is in play, because it calls into the regexp
matching engine potentially hundreds of times per file to be matched.
I've partly rolled back his change, so that we only call into the matcher
once per file, but preserved the ability to report a meaningful error
message if there's a syntax error in the regexp.
% init
% commit
adding 1/base
adding 2/base
% qnew mqbase
% qrefresh
% qdiff
diff -r b55ecdccb5cf 1/base
--- a/1/base
+++ b/1/base
@@ -1,1 +1,1 @@ base
-base
+patched
diff -r b55ecdccb5cf 2/base
--- a/2/base
+++ b/2/base
@@ -1,1 +1,1 @@ base
-base
+patched
% qdiff dirname
diff -r b55ecdccb5cf 1/base
--- a/1/base
+++ b/1/base
@@ -1,1 +1,1 @@ base
-base
+patched
diff -r b55ecdccb5cf 2/base
--- a/2/base
+++ b/2/base
@@ -1,1 +1,1 @@ base
-base
+patched
% patch file contents
mqbase
diff -r b55ecdccb5cf 1/base
--- a/1/base
+++ b/1/base
@@ -1,1 +1,1 @@ base
-base
+patched
diff -r b55ecdccb5cf 2/base
--- a/2/base
+++ b/2/base
@@ -1,1 +1,1 @@ base
-base
+patched
% qrefresh 1
% qdiff
diff -r b55ecdccb5cf 1/base
--- a/1/base
+++ b/1/base
@@ -1,1 +1,1 @@ base
-base
+patched
diff -r b55ecdccb5cf 2/base
--- a/2/base
+++ b/2/base
@@ -1,1 +1,1 @@ base
-base
+patched
% qdiff dirname
diff -r b55ecdccb5cf 1/base
--- a/1/base
+++ b/1/base
@@ -1,1 +1,1 @@ base
-base
+patched
diff -r b55ecdccb5cf 2/base
--- a/2/base
+++ b/2/base
@@ -1,1 +1,1 @@ base
-base
+patched
% patch file contents
mqbase
diff -r b55ecdccb5cf 1/base
--- a/1/base
+++ b/1/base
@@ -1,1 +1,1 @@ base
-base
+patched
% qrefresh . in subdir
% qdiff
diff -r b55ecdccb5cf 1/base
--- a/1/base
+++ b/1/base
@@ -1,1 +1,1 @@ base
-base
+patched
diff -r b55ecdccb5cf 2/base
--- a/2/base
+++ b/2/base
@@ -1,1 +1,1 @@ base
-base
+patched
% qdiff dirname
diff -r b55ecdccb5cf 1/base
--- a/1/base
+++ b/1/base
@@ -1,1 +1,1 @@ base
-base
+patched
diff -r b55ecdccb5cf 2/base
--- a/2/base
+++ b/2/base
@@ -1,1 +1,1 @@ base
-base
+patched
% patch file contents
mqbase
diff -r b55ecdccb5cf 1/base
--- a/1/base
+++ b/1/base
@@ -1,1 +1,1 @@ base
-base
+patched
% qrefresh in hg-root again
% qdiff
diff -r b55ecdccb5cf 1/base
--- a/1/base
+++ b/1/base
@@ -1,1 +1,1 @@ base
-base
+patched
diff -r b55ecdccb5cf 2/base
--- a/2/base
+++ b/2/base
@@ -1,1 +1,1 @@ base
-base
+patched
% qdiff dirname
diff -r b55ecdccb5cf 1/base
--- a/1/base
+++ b/1/base
@@ -1,1 +1,1 @@ base
-base
+patched
diff -r b55ecdccb5cf 2/base
--- a/2/base
+++ b/2/base
@@ -1,1 +1,1 @@ base
-base
+patched
% patch file contents
mqbase
diff -r b55ecdccb5cf 1/base
--- a/1/base
+++ b/1/base
@@ -1,1 +1,1 @@ base
-base
+patched
diff -r b55ecdccb5cf 2/base
--- a/2/base
+++ b/2/base
@@ -1,1 +1,1 @@ base
-base
+patched