From 9c3c22e2bf6cf05297556936666c8578e160c366 Mon Sep 17 00:00:00 2001 From: Jeff King Date: Mon, 6 Feb 2012 04:53:46 -0500 Subject: [PATCH] docs: add a basic description of the config API This wasn't documented at all; this is pretty bare-bones, but it should at least give new git hackers a basic idea of how the reading side works. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano --- Documentation/technical/api-config.txt | 101 +++++++++++++++++++++++++ 1 file changed, 101 insertions(+) create mode 100644 Documentation/technical/api-config.txt diff --git a/Documentation/technical/api-config.txt b/Documentation/technical/api-config.txt new file mode 100644 index 000000000..f428c5c48 --- /dev/null +++ b/Documentation/technical/api-config.txt @@ -0,0 +1,101 @@ +config API +========== + +The config API gives callers a way to access git configuration files +(and files which have the same syntax). See linkgit:git-config[1] for a +discussion of the config file syntax. + +General Usage +------------- + +Config files are parsed linearly, and each variable found is passed to a +caller-provided callback function. The callback function is responsible +for any actions to be taken on the config option, and is free to ignore +some options (it is not uncommon for the configuration to be parsed +several times during the run of a git program, with different callbacks +picking out different variables useful to themselves). + +A config callback function takes three parameters: + +- the name of the parsed variable. This is in canonical "flat" form: the + section, subsection, and variable segments will be separated by dots, + and the section and variable segments will be all lowercase. E.g., + `core.ignorecase`, `diff.SomeType.textconv`. + +- the value of the found variable, as a string. If the variable had no + value specified, the value will be NULL (typically this means it + should be interpreted as boolean true). + +- a void pointer passed in by the caller of the config API; this can + contain callback-specific data + +A config callback should return 0 for success, or -1 if the variable +could not be parsed properly. + +Basic Config Querying +--------------------- + +Most programs will simply want to look up variables in all config files +that git knows about, using the normal precedence rules. To do this, +call `git_config` with a callback function and void data pointer. + +`git_config` will read all config sources in order of increasing +priority. Thus a callback should typically overwrite previously-seen +entries with new ones (e.g., if both the user-wide `~/.gitconfig` and +repo-specific `.git/config` contain `color.ui`, the config machinery +will first feed the user-wide one to the callback, and then the +repo-specific one; by overwriting, the higher-priority repo-specific +value is left at the end). + +There is a special version of `git_config` called `git_config_early` +that takes an additional parameter to specify the repository config. +This should be used early in a git program when the repository location +has not yet been determined (and calling the usual lazy-evaluation +lookup rules would yield an incorrect location). + +Reading Specific Files +---------------------- + +To read a specific file in git-config format, use +`git_config_from_file`. This takes the same callback and data parameters +as `git_config`. + +Value Parsing Helpers +--------------------- + +To aid in parsing string values, the config API provides callbacks with +a number of helper functions, including: + +`git_config_int`:: +Parse the string to an integer, including unit factors. Dies on error; +otherwise, returns the parsed result. + +`git_config_ulong`:: +Identical to `git_config_int`, but for unsigned longs. + +`git_config_bool`:: +Parse a string into a boolean value, respecting keywords like "true" and +"false". Integer values are converted into true/false values (when they +are non-zero or zero, respectively). Other values cause a die(). If +parsing is successful, the return value is the result. + +`git_config_bool_or_int`:: +Same as `git_config_bool`, except that integers are returned as-is, and +an `is_bool` flag is unset. + +`git_config_maybe_bool`:: +Same as `git_config_bool`, except that it returns -1 on error rather +than dying. + +`git_config_string`:: +Allocates and copies the value string into the `dest` parameter; if no +string is given, prints an error message and returns -1. + +`git_config_pathname`:: +Similar to `git_config_string`, but expands `~` or `~user` into the +user's home directory when found at the beginning of the path. + +Writing Config Files +-------------------- + +TODO -- 2.26.2