Let 'make install' clear all cachefiles

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

Fix cache algorithm loophole

This closes the door for unneccessary calls to cgit_fill_cache().

Noticed by Linus.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

Add version identifier in generated files

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

Add license file and copyright notices

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

Add caching infrastructure

This enables internal caching of page output.

Page requests are split into four groups:
  1) repo listing (front page)
  2) repo summary
  3) repo pages w/symbolic references in query string
  4) repo pages w/constant sha1's in query string

Each group has a TTL specified in minutes. When a page is requested, a cached
filename is stat(2)'ed and st_mtime is compared to time(2). If TTL has expired
(or the file didn't exist), the cached file is regenerated.

When generating a cached file, locking is used to avoid parallell processing
of the request. If multiple processes tries to aquire the same lock, the ones
who fail to get the lock serves the (expired) cached file. If the cached file
don't exist, the process instead calls sched_yield(2) before restarting the
request processing.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

Add .gitignore

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

Replace useless make rules with generic $(OBJECTS) dependency

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

Import cgit prototype from git tree

This enables basic cgit functionality, using libgit.a and xdiff/lib.a from
git + a custom "git.h" + openssl for sha1 routines.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>