Merge branch 'ks/tree-diff-nway'

Instead of running N pair-wise diff-trees when inspecting a
N-parent merge, find the set of paths that were touched by walking
N+1 trees in parallel.  These set of paths can then be turned into
N pair-wise diff-tree results to be processed through rename
detections and such.  And N=2 case nicely degenerates to the usual
2-way diff-tree, which is very nice.

* ks/tree-diff-nway:
  mingw: activate alloca
  combine-diff: speed it up, by using multiparent diff tree-walker directly
  tree-diff: rework diff_tree() to generate diffs for multiparent cases as well
  Portable alloca for Git
  tree-diff: reuse base str(buf) memory on sub-tree recursion
  tree-diff: no need to call "full" diff_tree_sha1 from show_path()
  tree-diff: rework diff_tree interface to be sha1 based
  tree-diff: diff_tree() should now be static
  tree-diff: remove special-case diff-emitting code for empty-tree cases
  tree-diff: simplify tree_entry_pathcmp
  tree-diff: show_path prototype is not needed anymore
  tree-diff: rename compare_tree_entry -> tree_entry_pathcmp
  tree-diff: move all action-taking code out of compare_tree_entry()
  tree-diff: don't assume compare_tree_entry() returns -1,0,1
  tree-diff: consolidate code for emitting diffs and recursion in one place
  tree-diff: show_tree() is not needed
  tree-diff: no need to pass match to skip_uninteresting()
  tree-diff: no need to manually verify that there is no mode change for a path
  combine-diff: move changed-paths scanning logic into its own function
  combine-diff: move show_log_first logic/action out of paths scanning

1 files changed, 9 insertions, 2 deletions

diff --git a/diff.h b/diff.h
index a24a767..b4a624d 100644
--- a/diff.h
+++ b/diff.h
@@ -15,6 +15,10 @@ struct diff_filespec;
 struct userdiff_driver;
 struct sha1_array;
 struct commit;
+struct combine_diff_path;
+
+typedef int (*pathchange_fn_t)(struct diff_options *options,
+		 struct combine_diff_path *path);
 
 typedef void (*change_fn_t)(struct diff_options *options,
 		 unsigned old_mode, unsigned new_mode,
@@ -157,6 +161,7 @@ struct diff_options {
 	int close_file;
 
 	struct pathspec pathspec;
+	pathchange_fn_t pathchange;
 	change_fn_t change;
 	add_remove_fn_t add_remove;
 	diff_format_fn_t format_callback;
@@ -189,8 +194,10 @@ const char *diff_line_prefix(struct diff_options *);
 
 extern const char mime_boundary_leader[];
 
-extern int diff_tree(struct tree_desc *t1, struct tree_desc *t2,
-		     const char *base, struct diff_options *opt);
+extern struct combine_diff_path *diff_tree_paths(
+	struct combine_diff_path *p, const unsigned char *sha1,
+	const unsigned char **parent_sha1, int nparent,
+	struct strbuf *base, struct diff_options *opt);
 extern int diff_tree_sha1(const unsigned char *old, const unsigned char *new,
 			  const char *base, struct diff_options *opt);
 extern int diff_root_tree_sha1(const unsigned char *new, const char *base,