[PATCHv6 21/31] merge-recursive: add a new hashmap for storing file collisions

[Elijah Newren]

Directory renames with the ability to merge directories opens up the
possibility of add/add/add/.../add conflicts, if each of the N
directories being merged into one target directory all had a file with
the same name.  We need a way to check for and report on such
collisions; this hashmap will be used for this purpose.

Signed-off-by: Elijah Newren <new...@gmail.com>
---
 merge-recursive.c | 23 +++++++++++++++++++++++
 merge-recursive.h |  7 +++++++
 2 files changed, 30 insertions(+)

diff --git a/merge-recursive.c b/merge-recursive.c
index d92fba277..6bd4f34d5 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -84,6 +84,29 @@ static void dir_rename_entry_init(struct dir_rename_entry 
*entry,
        string_list_init(&entry->possible_new_dirs, 0);
 }
 
+static struct collision_entry *collision_find_entry(struct hashmap *hashmap,
+                                                   char *target_file)
+{
+       struct collision_entry key;
+
+       hashmap_entry_init(&key, strhash(target_file));
+       key.target_file = target_file;
+       return hashmap_get(hashmap, &key, NULL);
+}
+
+static int collision_cmp(void *unused_cmp_data,
+                        const struct collision_entry *e1,
+                        const struct collision_entry *e2,
+                        const void *unused_keydata)
+{
+       return strcmp(e1->target_file, e2->target_file);
+}
+
+static void collision_init(struct hashmap *map)
+{
+       hashmap_init(map, (hashmap_cmp_fn) collision_cmp, NULL, 0);
+}
+
 static void flush_output(struct merge_options *o)
 {
        if (o->buffer_output < 2 && o->obuf.len) {
diff --git a/merge-recursive.h b/merge-recursive.h
index d7f4cc80c..e1be27f57 100644
--- a/merge-recursive.h
+++ b/merge-recursive.h
@@ -37,6 +37,13 @@ struct dir_rename_entry {
        struct string_list possible_new_dirs;
 };
 
+struct collision_entry {
+       struct hashmap_entry ent; /* must be the first member! */
+       char *target_file;
+       struct string_list source_files;
+       unsigned reported_already:1;
+};
+
 /* merge_trees() but with recursive ancestor consolidation */
 int merge_recursive(struct merge_options *o,
                    struct commit *h1,
-- 
2.14.2