[PATCH] checkout: avoid unncessary match_pathspec calls

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

In checkout_paths() we do this

 - for i = 0..active_nr, if not updated, call match_pathspec
 - for ..., call match_pathspec (inside unmerge_cache)
 - for ..., call match_pathspec (for showing "path .. is unmerged)
 - for ..., if not updated, call match_pathspec and update paths

That's a lot of duplicate match_pathspec(s) and the function is not
exactly cheap to be called so many times, especially on large indexes.
This patch makes it call match_pathspec once per index entry, save the
result in ce_flags and reuse the results in the following loops.

This command is used on webkit, 215k entries. The pattern is chosen
mainly to make match_pathspec sweat:

git checkout -- "*[a-zA-Z]*[a-zA-Z]*[a-zA-Z]*"

        before      after
real    0m3.493s    0m2.737s
user    0m2.239s    0m1.586s
sys     0m1.252s    0m1.151s

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Junio, this patch clearly conflicts wih nd/magic-pathspecs. Do you
 want me to:

  - hold it off until nd/magic-pathspecs graduates
  - rebase on top of nd/magic-pathspecs and repost
  - leave it to you to handle conflicts

 ?

 builtin/checkout.c | 23 +++++++++++++++++++----
 cache.h            |  1 +
 resolve-undo.c     | 19 ++++++++++++++++++-
 resolve-undo.h     |  1 +
 4 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index a9c1b5a..fadc11b 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -273,22 +273,37 @@ static int checkout_paths(const struct checkout_opts *opts,
 
 	for (pos = 0; pos < active_nr; pos++) {
 		struct cache_entry *ce = active_cache[pos];
+		ce->ce_flags &= ~CE_MATCHED;
 		if (opts->source_tree && !(ce->ce_flags & CE_UPDATE))
 			continue;
-		match_pathspec(opts->pathspec, ce->name, ce_namelen(ce), 0, ps_matched);
+		if (match_pathspec(opts->pathspec, ce->name,
+				   ce_namelen(ce), 0, ps_matched))
+			ce->ce_flags |= CE_MATCHED;
 	}
 
 	if (report_path_error(ps_matched, opts->pathspec, opts->prefix))
 		return 1;
 
+	/*
+	 * call match_pathspec on the remaining entries that have not
+	 * been done in the previous loop
+	 */
+	for (pos = 0; pos < active_nr; pos++) {
+		struct cache_entry *ce = active_cache[pos];
+		if (opts->source_tree && !(ce->ce_flags & CE_UPDATE) &&
+		    match_pathspec(opts->pathspec, ce->name,
+				   ce_namelen(ce), 0, ps_matched))
+			ce->ce_flags |= CE_MATCHED;
+	}
+
 	/* "checkout -m path" to recreate conflicted state */
 	if (opts->merge)
-		unmerge_cache(opts->pathspec);
+		unmerge_marked_index(&the_index);
 
 	/* Any unmerged paths? */
 	for (pos = 0; pos < active_nr; pos++) {
 		struct cache_entry *ce = active_cache[pos];
-		if (match_pathspec(opts->pathspec, ce->name, ce_namelen(ce), 0, NULL)) {
+		if (ce->ce_flags & CE_MATCHED) {
 			if (!ce_stage(ce))
 				continue;
 			if (opts->force) {
@@ -315,7 +330,7 @@ static int checkout_paths(const struct checkout_opts *opts,
 		struct cache_entry *ce = active_cache[pos];
 		if (opts->source_tree && !(ce->ce_flags & CE_UPDATE))
 			continue;
-		if (match_pathspec(opts->pathspec, ce->name, ce_namelen(ce), 0, NULL)) {
+		if (ce->ce_flags & CE_MATCHED) {
 			if (!ce_stage(ce)) {
 				errs |= checkout_entry(ce, &state, NULL);
 				continue;
diff --git a/cache.h b/cache.h
index c56315c..04e6090 100644
--- a/cache.h
+++ b/cache.h
@@ -161,6 +161,7 @@ struct cache_entry {
 
 #define CE_UNPACKED          (1 << 24)
 #define CE_NEW_SKIP_WORKTREE (1 << 25)
+#define CE_MATCHED           (1 << 26)
 
 /*
  * Extended on-disk flags
diff --git a/resolve-undo.c b/resolve-undo.c
index 72b4612..639eb9c 100644
--- a/resolve-undo.c
+++ b/resolve-undo.c
@@ -118,7 +118,7 @@ int unmerge_index_entry_at(struct index_state *istate, int pos)
 	struct cache_entry *ce;
 	struct string_list_item *item;
 	struct resolve_undo_info *ru;
-	int i, err = 0;
+	int i, err = 0, matched;
 
 	if (!istate->resolve_undo)
 		return pos;
@@ -137,6 +137,7 @@ int unmerge_index_entry_at(struct index_state *istate, int pos)
 	ru = item->util;
 	if (!ru)
 		return pos;
+	matched = ce->ce_flags & CE_MATCHED;
 	remove_index_entry_at(istate, pos);
 	for (i = 0; i < 3; i++) {
 		struct cache_entry *nce;
@@ -144,6 +145,8 @@ int unmerge_index_entry_at(struct index_state *istate, int pos)
 			continue;
 		nce = make_cache_entry(ru->mode[i], ru->sha1[i],
 				       ce->name, i + 1, 0);
+		if (matched)
+			nce->ce_flags |= CE_MATCHED;
 		if (add_index_entry(istate, nce, ADD_CACHE_OK_TO_ADD)) {
 			err = 1;
 			error("cannot unmerge '%s'", ce->name);
@@ -156,6 +159,20 @@ int unmerge_index_entry_at(struct index_state *istate, int pos)
 	return unmerge_index_entry_at(istate, pos);
 }
 
+void unmerge_marked_index(struct index_state *istate)
+{
+	int i;
+
+	if (!istate->resolve_undo)
+		return;
+
+	for (i = 0; i < istate->cache_nr; i++) {
+		struct cache_entry *ce = istate->cache[i];
+		if (ce->ce_flags & CE_MATCHED)
+			i = unmerge_index_entry_at(istate, i);
+	}
+}
+
 void unmerge_index(struct index_state *istate, const char **pathspec)
 {
 	int i;
diff --git a/resolve-undo.h b/resolve-undo.h
index 8458769..7a30206 100644
--- a/resolve-undo.h
+++ b/resolve-undo.h
@@ -12,5 +12,6 @@ extern struct string_list *resolve_undo_read(const char *, unsigned long);
 extern void resolve_undo_clear_index(struct index_state *);
 extern int unmerge_index_entry_at(struct index_state *, int);
 extern void unmerge_index(struct index_state *, const char **);
+extern void unmerge_marked_index(struct index_state *);
 
 #endif
-- 
1.8.2.83.gc99314b