commit: allow partial commits with relative paths

In order to do partial commits, git-commit overlays a tree on the
cache and checks pathspecs against the result. Currently, the
overlaying is done using "prefix" which prevents relative pathspecs
with ".." and absolute pathspec from matching when they refer to
files not under "prefix" and absent from the index, but still in
the tree (i.e.  files staged for removal).

The point of providing a prefix at all is performance optimization.
If we say there is no common prefix for the files of interest, then
we have to read the entire tree into the index.

But even if we cannot use the working directory as a prefix, we can
still figure out if there is a common prefix for all given paths,
and use that instead. The pathspec_prefix() routine from ls-files.c
does exactly that.

Any use of global variables is removed from pathspec_prefix() so
that it can be called from commit.c.

Reported-by: Reuben Thomas <rrt@sc3d.org>
Analyzed-by: Michael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: Clemens Buchacher <drizzd@aon.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/cache.h b/cache.h
index e11cf6ab1c..553a6ebd4b 100644
--- a/cache.h
+++ b/cache.h
@@ -426,6 +426,7 @@ extern void set_git_work_tree(const char *tree);
 #define ALTERNATE_DB_ENVIRONMENT "GIT_ALTERNATE_OBJECT_DIRECTORIES"
 
 extern const char **get_pathspec(const char *prefix, const char **pathspec);
+extern const char *pathspec_prefix(const char *prefix, const char **pathspec);
 extern void setup_work_tree(void);
 extern const char *setup_git_directory_gently(int *);
 extern const char *setup_git_directory(void);