Ranged iterators and rewritten git_status_file

The goal of this work is to rewrite git_status_file to use the
same underlying code as git_status_foreach.

This is done in 3 phases:

1. Extend iterators to allow ranged iteration with start and
   end prefixes for the range of file names to be covered.
2. Improve diff so that when there is a pathspec and there is
   a common non-wildcard prefix of the pathspec, it will use
   ranged iterators to minimize excess iteration.
3. Rewrite git_status_file to call git_status_foreach_ext
   with a pathspec that covers just the one file being checked.

Since ranged iterators underlie the status & diff implementation,
this is actually fairly efficient.  The workdir iterator does
end up loading the contents of all the directories down to the
single file, which should ideally be avoided, but it is pretty
good.

1 files changed, 20 insertions, 11 deletions

diff --git a/include/git2/status.h b/include/git2/status.h
index 0aff56a65..0130b4011 100644
--- a/include/git2/status.h
+++ b/include/git2/status.h
@@ -36,15 +36,18 @@ GIT_BEGIN_DECL
 /**
  * Gather file statuses and run a callback for each one.
  *
- * The callback is passed the path of the file, the status and the data pointer
- * passed to this function. If the callback returns something other than
- * GIT_SUCCESS, this function will return that value.
+ * The callback is passed the path of the file, the status and the data
+ * pointer passed to this function. If the callback returns something other
+ * than 0, this function will return that value.
  *
  * @param repo a repository object
  * @param callback the function to call on each file
- * @return GIT_SUCCESS or the return value of the callback which did not return GIT_SUCCESS
+ * @return 0 on success or the return value of the callback that was non-zero
  */
-GIT_EXTERN(int) git_status_foreach(git_repository *repo, int (*callback)(const char *, unsigned int, void *), void *payload);
+GIT_EXTERN(int) git_status_foreach(
+	git_repository *repo,
+	int (*callback)(const char *, unsigned int, void *),
+	void *payload);
 
 /**
  * Select the files on which to report status.
@@ -115,7 +118,7 @@ typedef struct {
  */
 GIT_EXTERN(int) git_status_foreach_ext(
 	git_repository *repo,
-	git_status_options *opts,
+	const git_status_options *opts,
 	int (*callback)(const char *, unsigned int, void *),
 	void *payload);
 
@@ -129,7 +132,10 @@ GIT_EXTERN(int) git_status_foreach_ext(
  *		the file doesn't exist in any of HEAD, the index or the worktree,
  *		GIT_SUCCESS otherwise
  */
-GIT_EXTERN(int) git_status_file(unsigned int *status_flags, git_repository *repo, const char *path);
+GIT_EXTERN(int) git_status_file(
+	unsigned int *status_flags,
+	git_repository *repo,
+	const char *path);
 
 /**
  * Test if the ignore rules apply to a given file.
@@ -141,11 +147,14 @@ GIT_EXTERN(int) git_status_file(unsigned int *status_flags, git_repository *repo
  *
  * @param ignored boolean returning 0 if the file is not ignored, 1 if it is
  * @param repo a repository object
- * @param path the file to check ignores for, rooted at the repo's workdir
- * @return GIT_SUCCESS if the ignore rules could be processed for the file
- *		(regardless of whether it exists or not), or an error < 0 if they could not.
+ * @param path the file to check ignores for, rooted at the repo's workdir.
+ * @return 0 if ignore rules could be processed for the file (regardless
+ *         of whether it exists or not), or an error < 0 if they could not.
  */
-GIT_EXTERN(int) git_status_should_ignore(int *ignored, git_repository *repo, const char *path);
+GIT_EXTERN(int) git_status_should_ignore(
+	int *ignored,
+	git_repository *repo,
+	const char *path);
 
 /** @} */
 GIT_END_DECL