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.

1 files changed, 18 insertions, 2 deletions

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);