The code was using two string_lists, one for the directories and
one for the files.  The code never checks the lists independently
so we should be able to only use one list.  The string_list also
is a O(log n) for lookup and insertion.  Switching this to use a
hashmap will give O(1) which will save some time when there are
millions of paths that will be checked.

Also cleaned up a memory leak and method where the return was not
being used.

Signed-off-by: Kevin Willford <kewi...@microsoft.com>
---
 merge-recursive.c | 76 ++++++++++++++++++++++++++++++++++++++++---------------
 merge-recursive.h |  3 +--
 2 files changed, 57 insertions(+), 22 deletions(-)

diff --git a/merge-recursive.c b/merge-recursive.c
index 1494ffdb82..ebfe01017f 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -24,6 +24,31 @@
 #include "dir.h"
 #include "submodule.h"
 
+struct path_hashmap_entry {
+       struct hashmap_entry;
+       char path[FLEX_ARRAY];
+};
+
+static int path_hashmap_cmp(const void *cmp_data,
+                           const void *entry,
+                           const void *entry_or_key,
+                           const void *keydata)
+{
+       const struct path_hashmap_entry *a = entry;
+       const struct path_hashmap_entry *b = entry_or_key;
+       const char *key = keydata;
+
+       if (ignore_case)
+               return strcasecmp(a->path, key ? key : b->path);
+       else
+               return strcmp(a->path, key ? key : b->path);
+}
+
+static unsigned int path_hash(const char *path)
+{
+       return ignore_case ? strihash(path) : strhash(path);
+}
+
 static void flush_output(struct merge_options *o)
 {
        if (o->buffer_output < 2 && o->obuf.len) {
@@ -314,29 +339,25 @@ static int save_files_dirs(const unsigned char *sha1,
                struct strbuf *base, const char *path,
                unsigned int mode, int stage, void *context)
 {
+       struct path_hashmap_entry *entry;
        int baselen = base->len;
        struct merge_options *o = context;
 
        strbuf_addstr(base, path);
 
-       if (S_ISDIR(mode))
-               string_list_insert(&o->current_directory_set, base->buf);
-       else
-               string_list_insert(&o->current_file_set, base->buf);
+       FLEX_ALLOC_MEM(entry, path, base->buf, base->len);
+       hashmap_entry_init(entry, path_hash(entry->path));
+       hashmap_add(&o->current_file_dir_set, entry);
 
        strbuf_setlen(base, baselen);
        return (S_ISDIR(mode) ? READ_TREE_RECURSIVE : 0);
 }
 
-static int get_files_dirs(struct merge_options *o, struct tree *tree)
+static void get_files_dirs(struct merge_options *o, struct tree *tree)
 {
-       int n;
        struct pathspec match_all;
        memset(&match_all, 0, sizeof(match_all));
-       if (read_tree_recursive(tree, "", 0, 0, &match_all, save_files_dirs, o))
-               return 0;
-       n = o->current_file_set.nr + o->current_directory_set.nr;
-       return n;
+       read_tree_recursive(tree, "", 0, 0, &match_all, save_files_dirs, o);
 }
 
 /*
@@ -646,6 +667,7 @@ static void add_flattened_path(struct strbuf *out, const 
char *s)
 
 static char *unique_path(struct merge_options *o, const char *path, const char 
*branch)
 {
+       struct path_hashmap_entry *entry;
        struct strbuf newpath = STRBUF_INIT;
        int suffix = 0;
        size_t base_len;
@@ -654,14 +676,16 @@ static char *unique_path(struct merge_options *o, const 
char *path, const char *
        add_flattened_path(&newpath, branch);
 
        base_len = newpath.len;
-       while (string_list_has_string(&o->current_file_set, newpath.buf) ||
-              string_list_has_string(&o->current_directory_set, newpath.buf) ||
+       while (hashmap_get_from_hash(&o->current_file_dir_set,
+                                    path_hash(newpath.buf), newpath.buf) ||
               (!o->call_depth && file_exists(newpath.buf))) {
                strbuf_setlen(&newpath, base_len);
                strbuf_addf(&newpath, "_%d", suffix++);
        }
 
-       string_list_insert(&o->current_file_set, newpath.buf);
+       FLEX_ALLOC_MEM(entry, path, newpath.buf, newpath.len);
+       hashmap_entry_init(entry, path_hash(entry->path));
+       hashmap_add(&o->current_file_dir_set, entry);
        return strbuf_detach(&newpath, NULL);
 }
 
@@ -1945,8 +1969,14 @@ int merge_trees(struct merge_options *o,
        if (unmerged_cache()) {
                struct string_list *entries, *re_head, *re_merge;
                int i;
-               string_list_clear(&o->current_file_set, 1);
-               string_list_clear(&o->current_directory_set, 1);
+               /*
+                * Only need the hashmap while processing entries, so
+                * initialize it here and free it when we are done running
+                * through the entries. Keeping it in the merge_options as
+                * opposed to decaring a local hashmap is for convenience
+                * so that we don't have to pass it to around.
+                */
+               hashmap_init(&o->current_file_dir_set, path_hashmap_cmp, NULL, 
512);
                get_files_dirs(o, head);
                get_files_dirs(o, merge);
 
@@ -1956,7 +1986,7 @@ int merge_trees(struct merge_options *o,
                re_merge = get_renames(o, merge, common, head, merge, entries);
                clean = process_renames(o, re_head, re_merge);
                if (clean < 0)
-                       return clean;
+                       goto cleanup;
                for (i = entries->nr-1; 0 <= i; i--) {
                        const char *path = entries->items[i].string;
                        struct stage_data *e = entries->items[i].util;
@@ -1964,8 +1994,10 @@ int merge_trees(struct merge_options *o,
                                int ret = process_entry(o, path, e);
                                if (!ret)
                                        clean = 0;
-                               else if (ret < 0)
-                                       return ret;
+                               else if (ret < 0) {
+                                       clean = ret;
+                                       goto cleanup;
+                               }
                        }
                }
                for (i = 0; i < entries->nr; i++) {
@@ -1975,13 +2007,19 @@ int merge_trees(struct merge_options *o,
                                    entries->items[i].string);
                }
 
+cleanup:
                string_list_clear(re_merge, 0);
                string_list_clear(re_head, 0);
                string_list_clear(entries, 1);
 
+               hashmap_free(&o->current_file_dir_set, 1);
+
                free(re_merge);
                free(re_head);
                free(entries);
+
+               if (clean < 0)
+                       return clean;
        }
        else
                clean = 1;
@@ -2177,8 +2215,6 @@ void init_merge_options(struct merge_options *o)
        if (o->verbosity >= 5)
                o->buffer_output = 0;
        strbuf_init(&o->obuf, 0);
-       string_list_init(&o->current_file_set, 1);
-       string_list_init(&o->current_directory_set, 1);
        string_list_init(&o->df_conflict_file_set, 1);
 }
 
diff --git a/merge-recursive.h b/merge-recursive.h
index 735343b413..80d69d1401 100644
--- a/merge-recursive.h
+++ b/merge-recursive.h
@@ -25,8 +25,7 @@ struct merge_options {
        int show_rename_progress;
        int call_depth;
        struct strbuf obuf;
-       struct string_list current_file_set;
-       struct string_list current_directory_set;
+       struct hashmap current_file_dir_set;
        struct string_list df_conflict_file_set;
 };
 
-- 
2.14.1.327.g2b87382360.dirty

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