Some diff refactorings to help code reuse

There are some diff functions that are useful in a rewritten
checkout and this lays some groundwork for that.  This contains
three main things:

1. Share the function diff uses to calculate the OID for a file
   in the working directory (now named `git_diff__oid_for_file`
2. Add a `git_diff__paired_foreach` function to iterator over
   two diff lists concurrently.  Convert status to use it.
3. Move all the string/prefix/index entry comparisons into
   function pointers inside the `git_diff_list` object so they
   can be switched between case sensitive and insensitive
   versions.  This makes them easier to reuse in various
   functions without replicating logic.  As part of this, move
   a couple of index functions out of diff.c and into index.c.

11 files changed, 226 insertions, 127 deletions

diff --git a/src/attr_file.h b/src/attr_file.h
index 3ea13d273..5bdfc7054 100644
--- a/src/attr_file.h
+++ b/src/attr_file.h
@@ -7,6 +7,7 @@
 #ifndef INCLUDE_attr_file_h__
 #define INCLUDE_attr_file_h__
 
+#include "git2/oid.h"
 #include "git2/attr.h"
 #include "vector.h"
 #include "pool.h"
diff --git a/src/diff.c b/src/diff.c
index f3dfdd9dc..015c77edd 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -327,24 +327,39 @@ void git_diff_list_addref(git_diff_list *diff)
 	GIT_REFCOUNT_INC(diff);
 }
 
-static int oid_for_workdir_item(
+int git_diff__oid_for_file(
 	git_repository *repo,
-	const git_index_entry *item,
+	const char *path,
+	uint16_t  mode,
+	git_off_t size,
 	git_oid *oid)
 {
 	int result = 0;
 	git_buf full_path = GIT_BUF_INIT;
 
 	if (git_buf_joinpath(
-		&full_path, git_repository_workdir(repo), item->path) < 0)
+		&full_path, git_repository_workdir(repo), path) < 0)
 		return -1;
 
+	if (!mode) {
+		struct stat st;
+
+		if (p_stat(path, &st) < 0) {
+			giterr_set(GITERR_OS, "Could not stat '%s'", path);
+			result = -1;
+			goto cleanup;
+		}
+
+		mode = st.st_mode;
+		size = st.st_size;
+	}
+
 	/* calculate OID for file if possible */
-	if (S_ISGITLINK(item->mode)) {
+	if (S_ISGITLINK(mode)) {
 		git_submodule *sm;
 		const git_oid *sm_oid;
 
-		if (!git_submodule_lookup(&sm, repo, item->path) &&
+		if (!git_submodule_lookup(&sm, repo, path) &&
 			(sm_oid = git_submodule_wd_oid(sm)) != NULL)
 			git_oid_cpy(oid, sm_oid);
 		else {
@@ -354,23 +369,22 @@ static int oid_for_workdir_item(
 			giterr_clear();
 			memset(oid, 0, sizeof(*oid));
 		}
-	} else if (S_ISLNK(item->mode))
+	} else if (S_ISLNK(mode)) {
 		result = git_odb__hashlink(oid, full_path.ptr);
-	else if (!git__is_sizet(item->file_size)) {
-		giterr_set(GITERR_OS, "File size overflow for 32-bit systems");
+	} else if (!git__is_sizet(size)) {
+		giterr_set(GITERR_OS, "File size overflow (for 32-bits) on '%s'", path);
 		result = -1;
 	} else {
 		git_vector filters = GIT_VECTOR_INIT;
 
-		result = git_filters_load(
-			&filters, repo, item->path, GIT_FILTER_TO_ODB);
+		result = git_filters_load(&filters, repo, path, GIT_FILTER_TO_ODB);
 		if (result >= 0) {
 			int fd = git_futils_open_ro(full_path.ptr);
 			if (fd < 0)
 				result = fd;
 			else {
 				result = git_odb__hashfd_filtered(
-					oid, fd, (size_t)item->file_size, GIT_OBJ_BLOB, &filters);
+					oid, fd, (size_t)size, GIT_OBJ_BLOB, &filters);
 				p_close(fd);
 			}
 		}
@@ -378,8 +392,8 @@ static int oid_for_workdir_item(
 		git_filters_free(&filters);
 	}
 
+cleanup:
 	git_buf_free(&full_path);
-
 	return result;
 }
 
@@ -439,8 +453,7 @@ static int maybe_modified(
 	}
 
 	/* if oids and modes match, then file is unmodified */
-	else if (git_oid_cmp(&oitem->oid, &nitem->oid) == 0 &&
-			 omode == nmode)
+	else if (git_oid_equal(&oitem->oid, &nitem->oid) && omode == nmode)
 		status = GIT_DELTA_UNMODIFIED;
 
 	/* if we have an unknown OID and a workdir iterator, then check some
@@ -493,12 +506,14 @@ static int maybe_modified(
 	/* if we got here and decided that the files are modified, but we
 	 * haven't calculated the OID of the new item, then calculate it now
 	 */
-	if (status != GIT_DELTA_UNMODIFIED && git_oid_iszero(&nitem->oid)) {
-		if (oid_for_workdir_item(diff->repo, nitem, &noid) < 0)
+	if (status != GIT_DELTA_UNMODIFIED &&
+		git_oid_iszero(&nitem->oid) && !use_noid)
+	{
+		if (git_diff__oid_for_file(diff->repo,
+				nitem->path, nitem->mode, nitem->file_size, &noid) < 0)
 			return -1;
-		else if (omode == nmode && git_oid_equal(&oitem->oid, &noid))
+		if (omode == nmode && git_oid_equal(&oitem->oid, &noid))
 			status = GIT_DELTA_UNMODIFIED;
-
 		/* store calculated oid so we don't have to recalc later */
 		use_noid = &noid;
 	}
@@ -507,31 +522,14 @@ static int maybe_modified(
 		diff, status, oitem, omode, nitem, nmode, use_noid);
 }
 
-static int git_index_entry_cmp_case(const void *a, const void *b)
-{
-	const git_index_entry *entry_a = a;
-	const git_index_entry *entry_b = b;
-
-	return strcmp(entry_a->path, entry_b->path);
-}
-
-static int git_index_entry_cmp_icase(const void *a, const void *b)
-{
-	const git_index_entry *entry_a = a;
-	const git_index_entry *entry_b = b;
-
-	return strcasecmp(entry_a->path, entry_b->path);
-}
-
 static bool entry_is_prefixed(
+	git_diff_list *diff,
 	const git_index_entry *item,
-	git_iterator *prefix_iterator,
 	const git_index_entry *prefix_item)
 {
 	size_t pathlen;
 
-	if (!prefix_item ||
-		ITERATOR_PREFIXCMP(*prefix_iterator, prefix_item->path, item->path))
+	if (!prefix_item || diff->prefixcmp(prefix_item->path, item->path))
 		return false;
 
 	pathlen = strlen(item->path);
@@ -541,6 +539,35 @@ static bool entry_is_prefixed(
 			prefix_item->path[pathlen] == '/');
 }
 
+static int diff_list_init_from_iterators(
+	git_diff_list *diff,
+	git_iterator *old_iter,
+	git_iterator *new_iter)
+{
+	diff->old_src = old_iter->type;
+	diff->new_src = new_iter->type;
+
+	/* Use case-insensitive compare if either iterator has
+	 * the ignore_case bit set */
+	if (!old_iter->ignore_case && !new_iter->ignore_case) {
+		diff->opts.flags &= ~GIT_DIFF_DELTAS_ARE_ICASE;
+
+		diff->strcmp    = strcmp;
+		diff->strncmp   = strncmp;
+		diff->prefixcmp = git__prefixcmp;
+		diff->entrycmp  = git_index_entry__cmp;
+	} else {
+		diff->opts.flags |= GIT_DIFF_DELTAS_ARE_ICASE;
+
+		diff->strcmp    = strcasecmp;
+		diff->strncmp   = strncasecmp;
+		diff->prefixcmp = git__prefixcmp_icase;
+		diff->entrycmp  = git_index_entry__cmp_icase;
+	}
+
+	return 0;
+}
+
 static int diff_from_iterators(
 	git_repository *repo,
 	const git_diff_options *opts, /**< can be NULL for defaults */
@@ -548,37 +575,31 @@ static int diff_from_iterators(
 	git_iterator *new_iter,
 	git_diff_list **diff_ptr)
 {
+	int error = 0;
 	const git_index_entry *oitem, *nitem;
 	git_buf ignore_prefix = GIT_BUF_INIT;
 	git_diff_list *diff = git_diff_list_alloc(repo, opts);
-	git_vector_cmp entry_compare;
 
-	if (!diff)
-		goto fail;
-
-	diff->old_src = old_iter->type;
-	diff->new_src = new_iter->type;
+	*diff_ptr = NULL;
 
-	/* Use case-insensitive compare if either iterator has
-	 * the ignore_case bit set */
-	if (!old_iter->ignore_case && !new_iter->ignore_case) {
-		entry_compare = git_index_entry_cmp_case;
-		diff->opts.flags &= ~GIT_DIFF_DELTAS_ARE_ICASE;
-	} else {
-		entry_compare = git_index_entry_cmp_icase;
-		diff->opts.flags |= GIT_DIFF_DELTAS_ARE_ICASE;
+	if (!diff ||
+		diff_list_init_from_iterators(diff, old_iter, new_iter) < 0)
+		goto fail;
 
+	if (diff->opts.flags & GIT_DIFF_DELTAS_ARE_ICASE) {
 		/* If one of the iterators doesn't have ignore_case set,
 		 * then that's unfortunate because we'll have to spool
 		 * its data, sort it icase, and then use that for our
 		 * merge join to the other iterator that is icase sorted */
-		if (!old_iter->ignore_case) {
-			if (git_iterator_spoolandsort(&old_iter, old_iter, git_index_entry_cmp_icase, true) < 0)
-				goto fail;
-		} else if (!new_iter->ignore_case) {
-			if (git_iterator_spoolandsort(&new_iter, new_iter, git_index_entry_cmp_icase, true) < 0)
-				goto fail;
-		}
+		if (!old_iter->ignore_case &&
+			git_iterator_spoolandsort(
+				&old_iter, old_iter, diff->entrycmp, true) < 0)
+			goto fail;
+
+		if (!new_iter->ignore_case &&
+			git_iterator_spoolandsort(
+				&new_iter, new_iter, diff->entrycmp, true) < 0)
+			goto fail;
 	}
 
 	if (git_iterator_current(old_iter, &oitem) < 0 ||
@@ -589,7 +610,7 @@ static int diff_from_iterators(
 	while (oitem || nitem) {
 
 		/* create DELETED records for old items not matched in new */
-		if (oitem && (!nitem || entry_compare(oitem, nitem) < 0)) {
+		if (oitem && (!nitem || diff->entrycmp(oitem, nitem) < 0)) {
 			if (diff_delta__from_one(diff, GIT_DELTA_DELETED, oitem) < 0)
 				goto fail;
 
@@ -597,7 +618,7 @@ static int diff_from_iterators(
 			 * instead of just generating a DELETE record
 			 */
 			if ((diff->opts.flags & GIT_DIFF_INCLUDE_TYPECHANGE_TREES) != 0 &&
-				entry_is_prefixed(oitem, new_iter, nitem))
+				entry_is_prefixed(diff, oitem, nitem))
 			{
 				/* this entry has become a tree! convert to TYPECHANGE */
 				git_diff_delta *last = diff_delta__last_for_item(diff, oitem);
@@ -614,13 +635,12 @@ static int diff_from_iterators(
 		/* create ADDED, TRACKED, or IGNORED records for new items not
 		 * matched in old (and/or descend into directories as needed)
 		 */
-		else if (nitem && (!oitem || entry_compare(oitem, nitem) > 0)) {
+		else if (nitem && (!oitem || diff->entrycmp(oitem, nitem) > 0)) {
 			git_delta_t delta_type = GIT_DELTA_UNTRACKED;
 
 			/* check if contained in ignored parent directory */
 			if (git_buf_len(&ignore_prefix) &&
-				ITERATOR_PREFIXCMP(*old_iter, nitem->path,
-					git_buf_cstr(&ignore_prefix)) == 0)
+				diff->prefixcmp(nitem->path, git_buf_cstr(&ignore_prefix)) == 0)
 				delta_type = GIT_DELTA_IGNORED;
 
 			if (S_ISDIR(nitem->mode)) {
@@ -629,7 +649,7 @@ static int diff_from_iterators(
 				 * directories and it is not under an ignored directory.
 				 */
 				bool contains_tracked =
-					entry_is_prefixed(nitem, old_iter, oitem);
+					entry_is_prefixed(diff, nitem, oitem);
 				bool recurse_untracked =
 					(delta_type == GIT_DELTA_UNTRACKED &&
 					 (diff->opts.flags & GIT_DIFF_RECURSE_UNTRACKED_DIRS) != 0);
@@ -693,7 +713,7 @@ static int diff_from_iterators(
 			 */
 			if (delta_type != GIT_DELTA_IGNORED &&
 				(diff->opts.flags & GIT_DIFF_INCLUDE_TYPECHANGE_TREES) != 0 &&
-				entry_is_prefixed(nitem, old_iter, oitem))
+				entry_is_prefixed(diff, nitem, oitem))
 			{
 				/* this entry was a tree! convert to TYPECHANGE */
 				git_diff_delta *last = diff_delta__last_for_item(diff, oitem);
@@ -711,7 +731,7 @@ static int diff_from_iterators(
 		 * (or ADDED and DELETED pair if type changed)
 		 */
 		else {
-			assert(oitem && nitem && entry_compare(oitem, nitem) == 0);
+			assert(oitem && nitem && diff->entrycmp(oitem, nitem) == 0);
 
 			if (maybe_modified(old_iter, oitem, new_iter, nitem, diff) < 0 ||
 				git_iterator_advance(old_iter, &oitem) < 0 ||
@@ -720,21 +740,19 @@ static int diff_from_iterators(
 		}
 	}
 
-	git_iterator_free(old_iter);
-	git_iterator_free(new_iter);
-	git_buf_free(&ignore_prefix);
-
 	*diff_ptr = diff;
-	return 0;
 
 fail:
+	if (!*diff_ptr) {
+		git_diff_list_free(diff);
+		error = -1;
+	}
+
 	git_iterator_free(old_iter);
 	git_iterator_free(new_iter);
 	git_buf_free(&ignore_prefix);
 
-	git_diff_list_free(diff);
-	*diff_ptr = NULL;
-	return -1;
+	return error;
 }
 
 
diff --git a/src/diff.h b/src/diff.h
index ed66439bf..e9d8fd5a7 100644
--- a/src/diff.h
+++ b/src/diff.h
@@ -41,6 +41,11 @@ struct git_diff_list {
 	git_iterator_type_t old_src;
 	git_iterator_type_t new_src;
 	uint32_t diffcaps;
+
+	int (*strcmp)(const char *, const char *);
+	int (*strncmp)(const char *, const char *, size_t);
+	int (*prefixcmp)(const char *str, const char *pfx);
+	int (*entrycmp)(const void *a, const void *b);
 };
 
 extern void git_diff__cleanup_modes(
@@ -53,5 +58,8 @@ extern int git_diff_delta__cmp(const void *a, const void *b);
 extern bool git_diff_delta__should_skip(
 	const git_diff_options *opts, const git_diff_delta *delta);
 
+extern int git_diff__oid_for_file(
+	git_repository *, const char *, uint16_t, git_off_t, git_oid *);
+
 #endif
 
diff --git a/src/diff_output.c b/src/diff_output.c
index e678ec857..2f61540ff 100644
--- a/src/diff_output.c
+++ b/src/diff_output.c
@@ -1573,3 +1573,58 @@ int git_diff_patch_to_str(
 
 	return error;
 }
+
+int git_diff__paired_foreach(
+	git_diff_list *idx2head,
+	git_diff_list *wd2idx,
+	int (*cb)(void *cbref, git_diff_delta *i2h, git_diff_delta *w2i),
+	void *cbref)
+{
+	int cmp;
+	git_diff_delta *i2h, *w2i;
+	size_t i, j, i_max, j_max;
+	bool icase = false;
+
+	i_max = idx2head ? idx2head->deltas.length : 0;
+	j_max = wd2idx   ? wd2idx->deltas.length   : 0;
+
+	if (idx2head && wd2idx &&
+		(0 != (idx2head->opts.flags & GIT_DIFF_DELTAS_ARE_ICASE) ||
+		 0 != (wd2idx->opts.flags & GIT_DIFF_DELTAS_ARE_ICASE)))
+	{
+		/* Then use the ignore-case sorter... */
+		icase = true;
+
+		/* and assert that both are ignore-case sorted. If this function
+		 * ever needs to support merge joining result sets that are not sorted
+		 * by the same function, then it will need to be extended to do a spool
+		 * and sort on one of the results before merge joining */
+		assert(0 != (idx2head->opts.flags & GIT_DIFF_DELTAS_ARE_ICASE) &&
+			0 != (wd2idx->opts.flags & GIT_DIFF_DELTAS_ARE_ICASE));
+	}
+
+	for (i = 0, j = 0; i < i_max || j < j_max; ) {
+		i2h = idx2head ? GIT_VECTOR_GET(&idx2head->deltas,i) : NULL;
+		w2i = wd2idx   ? GIT_VECTOR_GET(&wd2idx->deltas,j)   : NULL;
+
+		cmp = !w2i ? -1 : !i2h ? 1 :
+			STRCMP_CASESELECT(icase, i2h->old_file.path, w2i->old_file.path);
+
+		if (cmp < 0) {
+			if (cb(cbref, i2h, NULL))
+				return GIT_EUSER;
+			i++;
+		} else if (cmp > 0) {
+			if (cb(cbref, NULL, w2i))
+				return GIT_EUSER;
+			j++;
+		} else {
+			if (cb(cbref, i2h, w2i))
+				return GIT_EUSER;
+			i++; j++;
+		}
+	}
+
+	return 0;
+}
+
diff --git a/src/diff_output.h b/src/diff_output.h
index 5fed1d998..f74dd3a71 100644
--- a/src/diff_output.h
+++ b/src/diff_output.h
@@ -83,4 +83,10 @@ typedef struct {
 	uint32_t diffed   : 1;
 } diff_delta_context;
 
+extern int git_diff__paired_foreach(
+	git_diff_list *idx2head,
+	git_diff_list *wd2idx,
+	int (*cb)(void *cbref, git_diff_delta *i2h, git_diff_delta *w2i),
+	void *cbref);
+
 #endif
diff --git a/src/index.c b/src/index.c
index 214d29def..c1b4565a3 100644
--- a/src/index.c
+++ b/src/index.c
@@ -516,7 +516,7 @@ git_index_entry *git_index_get_bypath(git_index *index, const char *path, int st
 	return git_index_get_byindex(index, pos);
 }
 
-void git_index__init_entry_from_stat(struct stat *st, git_index_entry *entry)
+void git_index_entry__init_from_stat(git_index_entry *entry, struct stat *st)
 {
 	entry->ctime.seconds = (git_time_t)st->st_ctime;
 	entry->mtime.seconds = (git_time_t)st->st_mtime;
@@ -530,6 +530,22 @@ void git_index__init_entry_from_stat(struct stat *st, git_index_entry *entry)
 	entry->file_size = st->st_size;
 }
 
+int git_index_entry__cmp(const void *a, const void *b)
+{
+	const git_index_entry *entry_a = a;
+	const git_index_entry *entry_b = b;
+
+	return strcmp(entry_a->path, entry_b->path);
+}
+
+int git_index_entry__cmp_icase(const void *a, const void *b)
+{
+	const git_index_entry *entry_a = a;
+	const git_index_entry *entry_b = b;
+
+	return strcasecmp(entry_a->path, entry_b->path);
+}
+
 static int index_entry_init(git_index_entry **entry_out, git_index *index, const char *rel_path)
 {
 	git_index_entry *entry = NULL;
@@ -568,7 +584,7 @@ static int index_entry_init(git_index_entry **entry_out, git_index *index, const
 	entry = git__calloc(1, sizeof(git_index_entry));
 	GITERR_CHECK_ALLOC(entry);
 
-	git_index__init_entry_from_stat(&st, entry);
+	git_index_entry__init_from_stat(entry, &st);
 
 	entry->oid = oid;
 	entry->path = git__strdup(rel_path);
diff --git a/src/index.h b/src/index.h
index 86158eb84..9778a543a 100644
--- a/src/index.h
+++ b/src/index.h
@@ -41,8 +41,11 @@ struct git_index {
 	git_vector_cmp reuc_search;
 };
 
-extern void git_index__init_entry_from_stat(struct stat *st, git_index_entry *entry);
+extern void git_index_entry__init_from_stat(git_index_entry *entry, struct stat *st);
 
 extern unsigned int git_index__prefix_position(git_index *index, const char *path);
 
+extern int git_index_entry__cmp(const void *a, const void *b);
+extern int git_index_entry__cmp_icase(const void *a, const void *b);
+
 #endif
diff --git a/src/iterator.c b/src/iterator.c
index 20878a060..33b775ce1 100644
--- a/src/iterator.c
+++ b/src/iterator.c
@@ -648,7 +648,7 @@ static int workdir_iterator__update_entry(workdir_iterator *wi)
 
 	wi->is_ignored = -1;
 
-	git_index__init_entry_from_stat(&ps->st, &wi->entry);
+	git_index_entry__init_from_stat(&wi->entry, &ps->st);
 
 	/* need different mode here to keep directories during iteration */
 	wi->entry.mode = git_futils_canonical_mode(ps->st.st_mode);
diff --git a/src/status.c b/src/status.c
index 2d022bfda..0bd170e6d 100644
--- a/src/status.c
+++ b/src/status.c
@@ -17,6 +17,7 @@
 
 #include "git2/diff.h"
 #include "diff.h"
+#include "diff_output.h"
 
 static unsigned int index_delta2status(git_delta_t index_status)
 {
@@ -76,21 +77,43 @@ static unsigned int workdir_delta2status(git_delta_t workdir_status)
 	return st;
 }
 
+typedef struct {
+	int (*cb)(const char *, unsigned int, void *);
+	void *cbdata;
+} status_user_callback;
+
+static int status_invoke_cb(
+	void *cbref, git_diff_delta *i2h, git_diff_delta *w2i)
+{
+	status_user_callback *usercb = cbref;
+	const char *path = NULL;
+	unsigned int status = 0;
+
+	if (w2i) {
+		path = w2i->old_file.path;
+		status |= workdir_delta2status(w2i->status);
+	}
+	if (i2h) {
+		path = i2h->old_file.path;
+		status |= index_delta2status(i2h->status);
+	}
+
+	return usercb->cb(path, status, usercb->cbdata);
+}
+
 int git_status_foreach_ext(
 	git_repository *repo,
 	const git_status_options *opts,
 	int (*cb)(const char *, unsigned int, void *),
 	void *cbdata)
 {
-	int err = 0, cmp;
+	int err = 0;
 	git_diff_options diffopt;
 	git_diff_list *idx2head = NULL, *wd2idx = NULL;
 	git_tree *head = NULL;
 	git_status_show_t show =
 		opts ? opts->show : GIT_STATUS_SHOW_INDEX_AND_WORKDIR;
-	git_diff_delta *i2h, *w2i;
-	size_t i, j, i_max, j_max;
-	bool ignore_case = false;
+	status_user_callback usercb;
 
 	assert(show <= GIT_STATUS_SHOW_INDEX_THEN_WORKDIR);
 
@@ -126,55 +149,19 @@ int git_status_foreach_ext(
 		(err = git_diff_workdir_to_index(repo, &diffopt, &wd2idx)) < 0)
 		goto cleanup;
 
+	usercb.cb = cb;
+	usercb.cbdata = cbdata;
+
 	if (show == GIT_STATUS_SHOW_INDEX_THEN_WORKDIR) {
-		for (i = 0; !err && i < idx2head->deltas.length; i++) {
-			i2h = GIT_VECTOR_GET(&idx2head->deltas, i);
-			if (cb(i2h->old_file.path, index_delta2status(i2h->status), cbdata))
-				err = GIT_EUSER;
-		}
+		if ((err = git_diff__paired_foreach(
+				 idx2head, NULL, status_invoke_cb, &usercb)) < 0)
+			goto cleanup;
+
 		git_diff_list_free(idx2head);
 		idx2head = NULL;
 	}
 
-	i_max = idx2head ? idx2head->deltas.length : 0;
-	j_max = wd2idx   ? wd2idx->deltas.length   : 0;
-
-	if (idx2head && wd2idx &&
-		(0 != (idx2head->opts.flags & GIT_DIFF_DELTAS_ARE_ICASE) ||
-		 0 != (wd2idx->opts.flags & GIT_DIFF_DELTAS_ARE_ICASE)))
-	{
-		/* Then use the ignore-case sorter... */
-		ignore_case = true;
-
-		/* and assert that both are ignore-case sorted. If this function
-		 * ever needs to support merge joining result sets that are not sorted
-		 * by the same function, then it will need to be extended to do a spool
-		 * and sort on one of the results before merge joining */
-		assert(0 != (idx2head->opts.flags & GIT_DIFF_DELTAS_ARE_ICASE) &&
-			0 != (wd2idx->opts.flags & GIT_DIFF_DELTAS_ARE_ICASE));
-	}
-
-	for (i = 0, j = 0; !err && (i < i_max || j < j_max); ) {
-		i2h = idx2head ? GIT_VECTOR_GET(&idx2head->deltas,i) : NULL;
-		w2i = wd2idx   ? GIT_VECTOR_GET(&wd2idx->deltas,j)   : NULL;
-
-		cmp = !w2i ? -1 : !i2h ? 1 : STRCMP_CASESELECT(ignore_case, i2h->old_file.path, w2i->old_file.path);
-
-		if (cmp < 0) {
-			if (cb(i2h->old_file.path, index_delta2status(i2h->status), cbdata))
-				err = GIT_EUSER;
-			i++;
-		} else if (cmp > 0) {
-			if (cb(w2i->old_file.path, workdir_delta2status(w2i->status), cbdata))
-				err = GIT_EUSER;
-			j++;
-		} else {
-			if (cb(i2h->old_file.path, index_delta2status(i2h->status) |
-				   workdir_delta2status(w2i->status), cbdata))
-				err = GIT_EUSER;
-			i++; j++;
-		}
-	}
+	err = git_diff__paired_foreach(idx2head, wd2idx, status_invoke_cb, &usercb);
 
 cleanup:
 	git_tree_free(head);
diff --git a/src/submodule.c b/src/submodule.c
index d69559dc2..1364b6881 100644
--- a/src/submodule.c
+++ b/src/submodule.c
@@ -371,7 +371,7 @@ int git_submodule_add_to_index(git_submodule *sm, int write_index)
 
 	memset(&entry, 0, sizeof(entry));
 	entry.path = sm->path;
-	git_index__init_entry_from_stat(&st, &entry);
+	git_index_entry__init_from_stat(&entry, &st);
 
 	/* calling git_submodule_open will have set sm->wd_oid if possible */
 	if ((sm->flags & GIT_SUBMODULE_STATUS__WD_OID_VALID) == 0) {
diff --git a/src/util.h b/src/util.h
index 3d00e9c85..23d4bc6e9 100644
--- a/src/util.h
+++ b/src/util.h
@@ -81,6 +81,11 @@ extern int git__prefixcmp(const char *str, const char *prefix);
 extern int git__prefixcmp_icase(const char *str, const char *prefix);
 extern int git__suffixcmp(const char *str, const char *suffix);
 
+GIT_INLINE(int) git__signum(int val)
+{
+	return ((val > 0) - (val < 0));
+}
+
 extern int git__strtol32(int32_t *n, const char *buff, const char **end_buf, int base);
 extern int git__strtol64(int64_t *n, const char *buff, const char **end_buf, int base);