Support Git over HTTP by proxying git-http-backend(1)git-http-backend

cgit lacks an easy way to support the "smart" HTTP protocol out of the
box. A patch [1] has been proposed in the past, but was never merged.
A few years later there was a short discussion at [2] which did not go
anywhere.

The majority of users who want to support the "smart" HTTP protocol
right now seem to conditionally point their web server to
git-http-backend(1) directly. This relies on proper path-matching and
regular expression support in the web server as seen in the EXMAPLES
section of git-http-backend(1).

As proposed in [3], it is possible to have cgit interface with the
necessary functionality in Git directly, but that would require more
work. It does not seem that this is something forthcoming in cgit.

Instead, for now, use a modified version of the patch suggested in [1],
which simply executes git-http-backend(1) when needed. This removes the
need for any additional plumbing in the web server.

Notable changes to the original patch:

 * Remove automatic handling of GIT_PROJECT_ROOT in favour of having the
   user set the variable correctly themselves. This reduces complexity.

 * Use the correct function to generate error pages. The original patch
   used html_status(), which does not exist anymore.

 * In cmd.c, adjust the struct entries to fit. Sadly we cannot use the
   def_cmd() macro directly, as the endpoints "git-upload-pack" and
   "git-receive-pack" contain dashes.

[1] https://lists.zx2c4.com/pipermail/cgit/2014-December/002312.html
[2] https://lists.zx2c4.com/pipermail/cgit/2016-February/002907.html
[3] https://lists.zx2c4.com/pipermail/cgit/2016-February/002926.html

1 files changed, 2 insertions, 0 deletions

diff --git a/ui-clone.h b/ui-clone.h
index 3e460a3..b27087e 100644
--- a/ui-clone.h
+++ b/ui-clone.h
@@ -4,5 +4,7 @@
 void cgit_clone_info(void);
 void cgit_clone_objects(void);
 void cgit_clone_head(void);
+void cgit_clone_git_upload_pack(void);
+void cgit_clone_git_receive_pack(void);
 
 #endif /* UI_CLONE_H */