Add explicit git_index ptr to diff and checkout

A number of diff APIs and the `git_checkout_index` API take a
`git_repository` object an operate on the index.  This updates
them to take a `git_index` pointer explicitly and only fall back
on the `git_repository` index if the index input is NULL.  This
makes it easier to operate on a temporary index.

7 files changed, 47 insertions, 38 deletions

diff --git a/src/checkout.c b/src/checkout.c
index bf1ff4f12..03536d446 100644
--- a/src/checkout.c
+++ b/src/checkout.c
@@ -601,12 +601,12 @@ static int checkout_create_submodules(
 
 int git_checkout_index(
 	git_repository *repo,
+	git_index *index,
 	git_checkout_opts *opts)
 {
 	git_diff_list *diff = NULL;
 	git_diff_options diff_opts = {0};
 	git_checkout_opts checkout_opts;
-
 	checkout_diff_data data;
 	git_buf workdir = GIT_BUF_INIT;
 	uint32_t *actions = NULL;
@@ -625,7 +625,7 @@ int git_checkout_index(
 	if (opts && opts->paths.count > 0)
 		diff_opts.pathspec = opts->paths;
 
-	if ((error = git_diff_workdir_to_index(&diff, repo, &diff_opts)) < 0)
+	if ((error = git_diff_workdir_to_index(&diff, repo, index, &diff_opts)) < 0)
 		goto cleanup;
 
 	if ((error = git_buf_puts(&workdir, git_repository_workdir(repo))) < 0)
@@ -706,12 +706,14 @@ int git_checkout_tree(
 		return -1;
 	}
 
+	/* TODO: create a temp index, load tree there and check it out */
+
 	/* load paths in tree that match pathspec into index */
 	if (!(error = git_repository_index(&index, repo)) &&
 		!(error = git_index_read_tree_match(
 			index, tree, opts ? &opts->paths : NULL)) &&
 		!(error = git_index_write(index)))
-		error = git_checkout_index(repo, opts);
+		error = git_checkout_index(repo, NULL, opts);
 
 	git_index_free(index);
 	git_tree_free(tree);
diff --git a/src/diff.c b/src/diff.c
index e6634e6d2..728e23712 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -753,15 +753,13 @@ fail:
 }
 
 
-#define DIFF_FROM_ITERATORS(SETUP, MAKE_FIRST, MAKE_SECOND) \
-	int error; \
+#define DIFF_FROM_ITERATORS(MAKE_FIRST, MAKE_SECOND) do { \
 	git_iterator *a = NULL, *b = NULL; \
 	char *pfx = opts ? git_pathspec_prefix(&opts->pathspec) : NULL; \
-	SETUP; \
     if (!(error = MAKE_FIRST) && !(error = MAKE_SECOND)) \
 		error = diff_from_iterators(diff, repo, a, b, opts); \
 	git__free(pfx); git_iterator_free(a); git_iterator_free(b); \
-    return error
+    } while (0)
 
 int git_diff_tree_to_tree(
 	git_diff_list **diff,
@@ -770,49 +768,59 @@ int git_diff_tree_to_tree(
 	git_tree *new_tree,
 	const git_diff_options *opts)
 {
+	int error = 0;
+
+	assert(diff && repo);
+
 	DIFF_FROM_ITERATORS(
-		assert(repo && old_tree && new_tree && diff),
 		git_iterator_for_tree_range(&a, repo, old_tree, pfx, pfx),
 		git_iterator_for_tree_range(&b, repo, new_tree, pfx, pfx)
 	);
-}
 
-int git_diff__tree_to_index(
-	git_diff_list **diff,
-	git_tree *tree,
-	git_index *index,
-	const git_diff_options *opts)
-{
-	DIFF_FROM_ITERATORS(
-		git_repository *repo = git_index_owner(index),
-	    git_iterator_for_index_range(&a, index, pfx, pfx),
-		git_iterator_for_tree_range(&b, repo, tree, pfx, pfx)
-	);
+	return error;
 }
 
 int git_diff_index_to_tree(
 	git_diff_list **diff,
 	git_repository *repo,
 	git_tree *old_tree,
+	git_index *index,
 	const git_diff_options *opts)
 {
+	int error = 0;
+
+	assert(diff && repo);
+
+	if (!index && (error = git_repository_index__weakptr(&index, repo)) < 0)
+		return error;
+
 	DIFF_FROM_ITERATORS(
-		assert(repo && diff),
 		git_iterator_for_tree_range(&a, repo, old_tree, pfx, pfx),
-	    git_iterator_for_repo_index_range(&b, repo, pfx, pfx)
+	    git_iterator_for_index_range(&b, index, pfx, pfx)
 	);
+
+	return error;
 }
 
 int git_diff_workdir_to_index(
 	git_diff_list **diff,
 	git_repository *repo,
+	git_index *index,
 	const git_diff_options *opts)
 {
+	int error = 0;
+
+	assert(diff && repo);
+
+	if (!index && (error = git_repository_index__weakptr(&index, repo)) < 0)
+		return error;
+
 	DIFF_FROM_ITERATORS(
-		assert(repo && diff),
-		git_iterator_for_repo_index_range(&a, repo, pfx, pfx),
+		git_iterator_for_index_range(&a, index, pfx, pfx),
 	    git_iterator_for_workdir_range(&b, repo, pfx, pfx)
 	);
+
+	return error;
 }
 
 
@@ -822,9 +830,14 @@ int git_diff_workdir_to_tree(
 	git_tree *old_tree,
 	const git_diff_options *opts)
 {
+	int error = 0;
+
+	assert(diff && repo);
+
 	DIFF_FROM_ITERATORS(
-		assert(repo && diff),
 		git_iterator_for_tree_range(&a, repo, old_tree, pfx, pfx),
 	    git_iterator_for_workdir_range(&b, repo, pfx, pfx)
 	);
+
+	return error;
 }
diff --git a/src/diff.h b/src/diff.h
index 3df7ce6d6..1e3be7593 100644
--- a/src/diff.h
+++ b/src/diff.h
@@ -61,11 +61,5 @@ extern bool git_diff_delta__should_skip(
 extern int git_diff__oid_for_file(
 	git_repository *, const char *, uint16_t, git_off_t, git_oid *);
 
-extern int git_diff__tree_to_index(
-	git_diff_list **diff,
-	git_tree *tree,
-	git_index *index,
-	const git_diff_options *opts);
-
 #endif
 
diff --git a/src/reset.c b/src/reset.c
index 69a9c4f04..8f470b26a 100644
--- a/src/reset.c
+++ b/src/reset.c
@@ -139,7 +139,7 @@ int git_reset(
 	memset(&opts, 0, sizeof(opts));
 	opts.checkout_strategy = GIT_CHECKOUT_FORCE;
 
-	if (git_checkout_index(repo, &opts) < 0) {
+	if (git_checkout_index(repo, NULL, &opts) < 0) {
 		giterr_set(GITERR_INDEX, "%s - Failed to checkout the index.", ERROR_MSG);
 		goto cleanup;
 	}
diff --git a/src/stash.c b/src/stash.c
index 2af3ca9fa..627d271f4 100644
--- a/src/stash.c
+++ b/src/stash.c
@@ -322,10 +322,10 @@ static int build_workdir_tree(
 	if (git_commit_tree(&b_tree, b_commit) < 0)
 		goto cleanup;
 
-	if (git_diff_index_to_tree(&diff, repo, b_tree, &opts) < 0)
+	if (git_diff_index_to_tree(&diff, repo, b_tree, NULL, &opts) < 0)
 		goto cleanup;
 
-	if (git_diff_workdir_to_index(&diff2, repo, &opts) < 0)
+	if (git_diff_workdir_to_index(&diff2, repo, NULL, &opts) < 0)
 		goto cleanup;
 
 	if (git_diff_merge(diff, diff2) < 0)
diff --git a/src/status.c b/src/status.c
index 9140ac2a8..b8c15ef92 100644
--- a/src/status.c
+++ b/src/status.c
@@ -142,11 +142,11 @@ int git_status_foreach_ext(
 	/* TODO: support EXCLUDE_SUBMODULES flag */
 
 	if (show != GIT_STATUS_SHOW_WORKDIR_ONLY &&
-		(err = git_diff_index_to_tree(&idx2head, repo, head, &diffopt)) < 0)
+		(err = git_diff_index_to_tree(&idx2head, repo, head, NULL, &diffopt)) < 0)
 		goto cleanup;
 
 	if (show != GIT_STATUS_SHOW_INDEX_ONLY &&
-		(err = git_diff_workdir_to_index(&wd2idx, repo, &diffopt)) < 0)
+		(err = git_diff_workdir_to_index(&wd2idx, repo, NULL, &diffopt)) < 0)
 		goto cleanup;
 
 	usercb.cb = cb;
diff --git a/src/submodule.c b/src/submodule.c
index 527d9e453..6eb1c52f7 100644
--- a/src/submodule.c
+++ b/src/submodule.c
@@ -1455,7 +1455,7 @@ static int submodule_wd_status(unsigned int *status, git_submodule *sm)
 		if (sm->ignore == GIT_SUBMODULE_IGNORE_NONE)
 			opt.flags |= GIT_DIFF_INCLUDE_UNTRACKED;
 
-		error = git_diff_index_to_tree(&diff, sm_repo, sm_head, &opt);
+		error = git_diff_index_to_tree(&diff, sm_repo, sm_head, NULL, &opt);
 
 		if (!error) {
 			if (git_diff_num_deltas(diff) > 0)
@@ -1472,7 +1472,7 @@ static int submodule_wd_status(unsigned int *status, git_submodule *sm)
 
 		/* perform index-to-workdir diff on submodule */
 
-		error = git_diff_workdir_to_index(&diff, sm_repo, &opt);
+		error = git_diff_workdir_to_index(&diff, sm_repo, NULL, &opt);
 
 		if (!error) {
 			size_t untracked =