[PATCH v3 0/3] git config cache & special querying api utilizing the cache

Hi,

[PATCH v3]: Added flag for NULL values that were causing segfaults in some cases.
	Added test-config for usage examples.
	Minor changes and corrections. Refer to discussion thread[5] for more details.
	Thanks to Matthieu, Jeff and Junio for their valuable suggestions.

[PATCH v2]:Changed the string_list to a struct instead of pointer to a struct.
	Added string-list initilization functions.
	Minor mistakes corrected acoording to review comments[4]. Thanks to
	Eric and Matthieu for their review.

[PATCH V1]:Most of the invaluable suggestions by Eric Sunshine, Torsten Bogershausen and
	Jeff King has been implemented[1]. Complete rewrite of config_cache*() family
	using git_config() as hook as suggested by Jeff. Thanks for the review.

[RFC V2]: Improved according to the suggestions by Eric Sunshine and Torsten Bogershausen.
	Added cache invalidation when config file is changed.[2]
	I am using git_config_set_multivar_in_file() as an update hook.

This is my first patch for this year's GSoC. My project is "Git Config API improvements". The link of my proposal is appended below [3].

The aim of this patch series is to generate a cache for querying values from the config files in a non-callback manner as the current method reads and parses the config files every time a value is queried for.

The cache is generated from hooking the update_cache function to the current parsing and callback mechanism in config.c. It is implemented as an hashmap using the hashmap-api with variables and its corresponding values list as its members. The values in the list are sorted in order of increasing priority. The cache is initialised the first time when any of the new query functions is called. It is invalidated by using git_config_set_multivar_in_file() as an update hook.

We add two new functions to the config-api, git_config_get_string() and git_config_get_string_multi() for querying in a non callback manner from the cache.

[1] http://marc.info/?t=140172066200006&r=1&w=2 [2] http://git.661346.n2.nabble.com/RFC-PATCH-0-2-Git-config-cache-amp-special-querying-api-utilizing-the-cache-td7611691.html [3] https://drive.google.com/file/d/0B4suZ-aHqDcnSUZJRXVTTnZUN1E/edit?usp=sharing [4] http://thread.gmane.org/gmane.comp.version-control.git/251073/focus=251369 [5] http://thread.gmane.org/gmane.comp.version-control.git/251704/

Tanay Abhra (3):
  string-list: Add string_list initializer helper functions
  config: Add hashtable for config parsing & retrieval
  test-config

 .gitignore                             |   1 +
 Documentation/technical/api-config.txt |  26 ++++++
 Makefile                               |   1 +
 cache.h                                |   2 +
 config.c                               | 144 +++++++++++++++++++++++++++++++++
 string-list.c                          |  18 +++++
 string-list.h                          |   3 +
 test-config.c                          |  93 +++++++++++++++++++++
 8 files changed, 288 insertions(+)
 create mode 100644 test-config.c