merge-ort: implement compute_rename_counts()

This function is based on the first half of get_directory_renames() from
merge-recursive.c; as part of the implementation, factor out a routine,
increment_count(), to update the bookkeeping to track the number of
items renamed into new directories.

Signed-off-by: Elijah Newren <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: newren

merge-ort.c

@@ -721,7 +721,6 @@ static int handle_content_merge(struct merge_options *opt,
 
 /*** Function Grouping: functions related to directory rename detection ***/
 
-MAYBE_UNUSED
 static void get_renamed_dir_portion(const char *old_path, const char *new_path,
 				    char **old_dir, char **new_dir)
 {
@@ -825,11 +824,62 @@ static void get_renamed_dir_portion(const char *old_path, const char *new_path,
 	*new_dir = xstrndup(new_path, end_of_new - new_path);
 }
 
+static void increment_count(struct strmap *dir_rename_count,
+			    char *old_dir,
+			    char *new_dir)
+{
+	struct strintmap *counts;
+	struct strmap_entry *e;
+
+	/* Get the {new_dirs -> counts} mapping using old_dir */
+	e = strmap_get_entry(dir_rename_count, old_dir);
+	if (e) {
+		counts = e->value;
+	} else {
+		counts = xmalloc(sizeof(*counts));
+		strintmap_init_with_options(counts, 0, NULL, 1);
+		strmap_put(dir_rename_count, old_dir, counts);
+	}
+
+	/* Increment the count for new_dir */
+	strintmap_incr(counts, new_dir, 1);
+}
+
 static void compute_rename_counts(struct diff_queue_struct *pairs,
 				  struct strmap *dir_rename_count,
 				  struct strset *dirs_removed)
 {
-	die("Not yet implemented!");
+	int i;
+
+	for (i = 0; i < pairs->nr; ++i) {
+		char *old_dir, *new_dir;
+		struct diff_filepair *pair = pairs->queue[i];
+
+		/* File not part of directory rename if it wasn't renamed */
+		if (pair->status != 'R')
+			continue;
+
+		/* Get the old and new directory names */
+		get_renamed_dir_portion(pair->one->path, pair->two->path,
+					&old_dir,        &new_dir);
+		if (!old_dir)
+			/* Directory didn't change at all; ignore this one. */
+			continue;
+
+		/*
+		 * Make dir_rename_count contain a map of a map:
+		 *   old_directory -> {new_directory -> count}
+		 * In other words, for every pair look at the directories for
+		 * the old filename and the new filename and count how many
+		 * times that pairing occurs.
+		 */
+		if (strset_contains(dirs_removed, old_dir))
+			increment_count(dir_rename_count, old_dir, new_dir);
+
+		/* Free resources we don't need anymore */
+		free(old_dir);
+		free(new_dir);
+	}
 }
 
 static void get_provisional_directory_renames(struct merge_options *opt,