Re: [PATCH 2/2] diff_index: honor in-index, not working-tree, .gitattributes

On Thu, Sep 22, 2011 at 8:38 PM, Jay Soffian [off-list ref] wrote:

On Thu, Sep 22, 2011 at 6:39 PM, Junio C Hamano [off-list ref] wrote:

quoted

I think the logical conclusion of assuming that we will keep the "single
source only" semantics (which I think we will, by the way, unless I hear a
concrete proposal to how we apply attributes from more than one sources in
what way to which side of the diff) is that a patch might be an
improvement over the current behaviour if it teaches "diff-tree" to read
from the tree and populate the in-core index (never writing it out to
$GIT_DIR/index) from the postimage tree (i.e. "diff preimage postimage" or
"diff -R postimage preimage") when it is run in a bare repository.

Okay, I can give that a try.

This area of git is still black magic to me. My best guess is
something like this:

diff --git a/tree-diff.c b/tree-diff.c
index b3cc2e4753..6fd84eb2bb 100644
--- a/tree-diff.c
+++ b/tree-diff.c

@@ -5,6 +5,8 @@
 #include "diff.h"
 #include "diffcore.h"
 #include "tree.h"
+#include "attr.h"
+#include "unpack-trees.h"

 static void show_entry(struct diff_options *opt, const char *prefix,
 		       struct tree_desc *desc, struct strbuf *base);

@@ -280,6 +282,19 @@ int diff_tree_sha1(const unsigned char *old,

const unsigned char *new, const cha
 		die("unable to read destination tree (%s)", sha1_to_hex(new));
 	init_tree_desc(&t1, tree1, size1);
 	init_tree_desc(&t2, tree2, size2);
+
+	if (is_bare_repository()) {
+		struct unpack_trees_options unpack_opts;
+		memset(&unpack_opts, 0, sizeof(unpack_opts));
+		unpack_opts.index_only = 1;
+		unpack_opts.head_idx = -1;
+		unpack_opts.src_index = &the_index;
+		unpack_opts.dst_index = &the_index;
+		unpack_opts.fn = oneway_merge;
+		if (unpack_trees(1, DIFF_OPT_TST(opt, REVERSE_DIFF) ? &t1 : &t2,
&unpack_opts) == 0)
+			git_attr_set_direction(GIT_ATTR_INDEX, &the_index);
+	}
+
 	retval = diff_tree(&t1, &t2, base, opt);
 	if (!*base && DIFF_OPT_TST(opt, FOLLOW_RENAMES) && diff_might_be_rename()) {
 		init_tree_desc(&t1, tree1, size1);

(And in case gmail line wraps that -- https://gist.github.com/1236806)

Am I barking up the right tree? (Obviously still needs tests, and
maybe an --[no]-tree-attributes option.)

j.