Add git_config_refresh() API to reload config

This adds a new API that allows users to reload the config if the
file has changed on disk.  A new config callback function to
refresh the config was added.

The modified time and file size are used to test if the file needs
to be reloaded (and are now stored in the disk backend object).

In writing tests, just using mtime was a problem / race, so I
wanted to check file size as well.  To support that, I extended
`git_futils_readbuffer_updated` to optionally check file size in
addition to mtime, and I added a new function `git_filebuf_stats`
to fetch the mtime and size for an open filebuf (so that the
config could be easily refreshed after a write).

Lastly, I moved some similar file checking code for attributes
into filebuf.  It is still only being used for attrs, but it
seems potentially reusable, so I thought I'd move it over.

1 files changed, 24 insertions, 1 deletions

diff --git a/src/fileops.h b/src/fileops.h
index 19f7ffd54..6437ccc45 100644
--- a/src/fileops.h
+++ b/src/fileops.h
@@ -18,7 +18,8 @@
  * Read whole files into an in-memory buffer for processing
  */
 extern int git_futils_readbuffer(git_buf *obj, const char *path);
-extern int git_futils_readbuffer_updated(git_buf *obj, const char *path, time_t *mtime, int *updated);
+extern int git_futils_readbuffer_updated(
+	git_buf *obj, const char *path, time_t *mtime, size_t *size, int *updated);
 extern int git_futils_readbuffer_fd(git_buf *obj, git_file fd, size_t len);
 
 /**
@@ -266,4 +267,26 @@ extern int git_futils_find_system_file(git_buf *path, const char *filename);
  */
 extern int git_futils_fake_symlink(const char *new, const char *old);
 
+
+typedef struct {
+	git_time_t seconds;
+	git_off_t  size;
+	unsigned int ino;
+} git_futils_stat_sig;
+
+/**
+ * Compare stat information for file with reference info.
+ *
+ * Use this as a way to track if a file has changed on disk.  This will
+ * return GIT_ENOTFOUND if the file doesn't exist, 0 if the file is up-to-date
+ * with regards to the signature, and 1 if the file needs to reloaded.  When
+ * a 1 is returned, the signature will also be updated with the latest data.
+ *
+ * @param sig stat signature structure
+ * @param path path to be statted
+ * @return 0 if up-to-date, 1 if out-of-date, <0 on error
+ */
+extern int git_futils_stat_sig_needs_reload(
+	git_futils_stat_sig *sig, const char *path);
+
 #endif /* INCLUDE_fileops_h__ */