Merge branch 'en/rename-directory-detection'

Rename detection logic in "diff" family that is used in "merge" has
learned to guess when all of x/a, x/b and x/c have moved to z/a,
z/b and z/c, it is likely that x/d added in the meantime would also
want to move to z/d by taking the hint that the entire directory
'x' moved to 'z'.  A bug causing dirty files involved in a rename
to be overwritten during merge has also been fixed as part of this
work.

* en/rename-directory-detection: (29 commits)
  merge-recursive: ensure we write updates for directory-renamed file
  merge-recursive: avoid spurious rename/rename conflict from dir renames
  directory rename detection: new testcases showcasing a pair of bugs
  merge-recursive: fix remaining directory rename + dirty overwrite cases
  merge-recursive: fix overwriting dirty files involved in renames
  merge-recursive: avoid clobbering untracked files with directory renames
  merge-recursive: apply necessary modifications for directory renames
  merge-recursive: when comparing files, don't include trees
  merge-recursive: check for file level conflicts then get new name
  merge-recursive: add computation of collisions due to dir rename & merging
  merge-recursive: check for directory level conflicts
  merge-recursive: add get_directory_renames()
  merge-recursive: make a helper function for cleanup for handle_renames
  merge-recursive: split out code for determining diff_filepairs
  merge-recursive: make !o->detect_rename codepath more obvious
  merge-recursive: fix leaks of allocated renames and diff_filepairs
  merge-recursive: introduce new functions to handle rename logic
  merge-recursive: move the get_renames() function
  directory rename detection: tests for handling overwriting dirty files
  directory rename detection: tests for handling overwriting untracked files
  ...

merge-recursive.h

 #ifndef MERGE_RECURSIVE_H
 #define MERGE_RECURSIVE_H
 
+#include "unpack-trees.h"
 #include "string-list.h"
 
 struct merge_options {
@@ -27,6 +28,32 @@ struct merge_options {
 	struct strbuf obuf;
 	struct hashmap current_file_dir_set;
 	struct string_list df_conflict_file_set;
+	struct unpack_trees_options unpack_opts;
+};
+
+/*
+ * For dir_rename_entry, directory names are stored as a full path from the
+ * toplevel of the repository and do not include a trailing '/'.  Also:
+ *
+ *   dir:                original name of directory being renamed
+ *   non_unique_new_dir: if true, could not determine new_dir
+ *   new_dir:            final name of directory being renamed
+ *   possible_new_dirs:  temporary used to help determine new_dir; see comments
+ *                       in get_directory_renames() for details
+ */
+struct dir_rename_entry {
+	struct hashmap_entry ent; /* must be the first member! */
+	char *dir;
+	unsigned non_unique_new_dir:1;
+	struct strbuf new_dir;
+	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 */

strbuf.c

 #include "cache.h"
 #include "refs.h"
+#include "string-list.h"
 #include "utf8.h"
 
 int starts_with(const char *str, const char *prefix)
@@ -171,6 +172,21 @@ struct strbuf **strbuf_split_buf(const char *str, size_t slen,
 	return ret;
 }
 
+void strbuf_add_separated_string_list(struct strbuf *str,
+				      const char *sep,
+				      struct string_list *slist)
+{
+	struct string_list_item *item;
+	int sep_needed = 0;
+
+	for_each_string_list_item(item, slist) {
+		if (sep_needed)
+			strbuf_addstr(str, sep);
+		strbuf_addstr(str, item->string);
+		sep_needed = 1;
+	}
+}
+
 void strbuf_list_free(struct strbuf **sbs)
 {
 	struct strbuf **s = sbs;

strbuf.h

 #ifndef STRBUF_H
 #define STRBUF_H
 
+struct string_list;
+
 /**
  * strbuf's are meant to be used with all the usual C string and memory
  * APIs. Given that the length of the buffer is known, it's often better to
@@ -531,6 +533,20 @@ static inline struct strbuf **strbuf_split(const struct strbuf *sb,
 	return strbuf_split_max(sb, terminator, 0);
 }
 
+/*
+ * Adds all strings of a string list to the strbuf, separated by the given
+ * separator.  For example, if sep is
+ *   ', '
+ * and slist contains
+ *   ['element1', 'element2', ..., 'elementN'],
+ * then write:
+ *   'element1, element2, ..., elementN'
+ * to str.  If only one element, just write "element1" to str.
+ */
+extern void strbuf_add_separated_string_list(struct strbuf *str,
+					     const char *sep,
+					     struct string_list *slist);
+
 /**
  * Free a NULL-terminated list of strbufs (for example, the return
  * values of the strbuf_split*() functions).

t/t3501-revert-cherry-pick.sh

@@ -141,7 +141,7 @@ test_expect_success 'cherry-pick "-" works with arguments' '
 	test_cmp expect actual
 '
 
-test_expect_failure 'cherry-pick works with dirty renamed file' '
+test_expect_success 'cherry-pick works with dirty renamed file' '
 	test_commit to-rename &&
 	git checkout -b unrelated &&
 	test_commit unrelated &&

t/t7607-merge-overwrite.sh

@@ -92,7 +92,7 @@ test_expect_success 'will not overwrite removed file with staged changes' '
 	test_cmp important c1.c
 '
 
-test_expect_failure 'will not overwrite unstaged changes in renamed file' '
+test_expect_success 'will not overwrite unstaged changes in renamed file' '
 	git reset --hard c1 &&
 	git mv c1.c other.c &&
 	git commit -m rename &&

unpack-trees.c

@@ -1509,8 +1509,8 @@ static int verify_uptodate_1(const struct cache_entry *ce,
 		add_rejected_path(o, error_type, ce->name);
 }
 
-static int verify_uptodate(const struct cache_entry *ce,
-			   struct unpack_trees_options *o)
+int verify_uptodate(const struct cache_entry *ce,
+		    struct unpack_trees_options *o)
 {
 	if (!o->skip_sparse_checkout && (ce->ce_flags & CE_NEW_SKIP_WORKTREE))
 		return 0;

unpack-trees.h

 #ifndef UNPACK_TREES_H
 #define UNPACK_TREES_H
 
+#include "tree-walk.h"
 #include "string-list.h"
 
 #define MAX_UNPACK_TREES 8
@@ -78,6 +79,9 @@ struct unpack_trees_options {
 extern int unpack_trees(unsigned n, struct tree_desc *t,
 		struct unpack_trees_options *options);
 
+int verify_uptodate(const struct cache_entry *ce,
+		    struct unpack_trees_options *o);
+
 int threeway_merge(const struct cache_entry * const *stages,
 		   struct unpack_trees_options *o);
 int twoway_merge(const struct cache_entry * const *src,