319 lines
13 KiB
Text
319 lines
13 KiB
Text
config API
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==========
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The config API gives callers a way to access Git configuration files
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(and files which have the same syntax). See linkgit:git-config[1] for a
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discussion of the config file syntax.
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General Usage
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-------------
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Config files are parsed linearly, and each variable found is passed to a
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caller-provided callback function. The callback function is responsible
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for any actions to be taken on the config option, and is free to ignore
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some options. It is not uncommon for the configuration to be parsed
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several times during the run of a Git program, with different callbacks
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picking out different variables useful to themselves.
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A config callback function takes three parameters:
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- the name of the parsed variable. This is in canonical "flat" form: the
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section, subsection, and variable segments will be separated by dots,
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and the section and variable segments will be all lowercase. E.g.,
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`core.ignorecase`, `diff.SomeType.textconv`.
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- the value of the found variable, as a string. If the variable had no
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value specified, the value will be NULL (typically this means it
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should be interpreted as boolean true).
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- a void pointer passed in by the caller of the config API; this can
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contain callback-specific data
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A config callback should return 0 for success, or -1 if the variable
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could not be parsed properly.
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Basic Config Querying
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---------------------
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Most programs will simply want to look up variables in all config files
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that Git knows about, using the normal precedence rules. To do this,
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call `git_config` with a callback function and void data pointer.
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`git_config` will read all config sources in order of increasing
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priority. Thus a callback should typically overwrite previously-seen
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entries with new ones (e.g., if both the user-wide `~/.gitconfig` and
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repo-specific `.git/config` contain `color.ui`, the config machinery
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will first feed the user-wide one to the callback, and then the
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repo-specific one; by overwriting, the higher-priority repo-specific
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value is left at the end).
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The `config_with_options` function lets the caller examine config
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while adjusting some of the default behavior of `git_config`. It should
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almost never be used by "regular" Git code that is looking up
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configuration variables. It is intended for advanced callers like
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`git-config`, which are intentionally tweaking the normal config-lookup
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process. It takes two extra parameters:
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`config_source`::
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If this parameter is non-NULL, it specifies the source to parse for
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configuration, rather than looking in the usual files. See `struct
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git_config_source` in `config.h` for details. Regular `git_config` defaults
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to `NULL`.
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`opts`::
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Specify options to adjust the behavior of parsing config files. See `struct
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config_options` in `config.h` for details. As an example: regular `git_config`
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sets `opts.respect_includes` to `1` by default.
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Reading Specific Files
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----------------------
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To read a specific file in git-config format, use
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`git_config_from_file`. This takes the same callback and data parameters
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as `git_config`.
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Querying For Specific Variables
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-------------------------------
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For programs wanting to query for specific variables in a non-callback
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manner, the config API provides two functions `git_config_get_value`
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and `git_config_get_value_multi`. They both read values from an internal
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cache generated previously from reading the config files.
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`int git_config_get_value(const char *key, const char **value)`::
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Finds the highest-priority value for the configuration variable `key`,
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stores the pointer to it in `value` and returns 0. When the
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configuration variable `key` is not found, returns 1 without touching
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`value`. The caller should not free or modify `value`, as it is owned
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by the cache.
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`const struct string_list *git_config_get_value_multi(const char *key)`::
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Finds and returns the value list, sorted in order of increasing priority
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for the configuration variable `key`. When the configuration variable
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`key` is not found, returns NULL. The caller should not free or modify
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the returned pointer, as it is owned by the cache.
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`void git_config_clear(void)`::
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Resets and invalidates the config cache.
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The config API also provides type specific API functions which do conversion
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as well as retrieval for the queried variable, including:
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`int git_config_get_int(const char *key, int *dest)`::
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Finds and parses the value to an integer for the configuration variable
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`key`. Dies on error; otherwise, stores the value of the parsed integer in
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`dest` and returns 0. When the configuration variable `key` is not found,
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returns 1 without touching `dest`.
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`int git_config_get_ulong(const char *key, unsigned long *dest)`::
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Similar to `git_config_get_int` but for unsigned longs.
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`int git_config_get_bool(const char *key, int *dest)`::
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Finds and parses the value into a boolean value, for the configuration
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variable `key` respecting keywords like "true" and "false". Integer
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values are converted into true/false values (when they are non-zero or
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zero, respectively). Other values cause a die(). If parsing is successful,
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stores the value of the parsed result in `dest` and returns 0. When the
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configuration variable `key` is not found, returns 1 without touching
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`dest`.
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`int git_config_get_bool_or_int(const char *key, int *is_bool, int *dest)`::
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Similar to `git_config_get_bool`, except that integers are copied as-is,
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and `is_bool` flag is unset.
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`int git_config_get_maybe_bool(const char *key, int *dest)`::
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Similar to `git_config_get_bool`, except that it returns -1 on error
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rather than dying.
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`int git_config_get_string_const(const char *key, const char **dest)`::
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Allocates and copies the retrieved string into the `dest` parameter for
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the configuration variable `key`; if NULL string is given, prints an
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error message and returns -1. When the configuration variable `key` is
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not found, returns 1 without touching `dest`.
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`int git_config_get_string(const char *key, char **dest)`::
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Similar to `git_config_get_string_const`, except that retrieved value
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copied into the `dest` parameter is a mutable string.
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`int git_config_get_pathname(const char *key, const char **dest)`::
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Similar to `git_config_get_string`, but expands `~` or `~user` into
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the user's home directory when found at the beginning of the path.
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`git_die_config(const char *key, const char *err, ...)`::
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First prints the error message specified by the caller in `err` and then
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dies printing the line number and the file name of the highest priority
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value for the configuration variable `key`.
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`void git_die_config_linenr(const char *key, const char *filename, int linenr)`::
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Helper function which formats the die error message according to the
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parameters entered. Used by `git_die_config()`. It can be used by callers
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handling `git_config_get_value_multi()` to print the correct error message
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for the desired value.
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See test-config.c for usage examples.
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Value Parsing Helpers
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---------------------
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To aid in parsing string values, the config API provides callbacks with
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a number of helper functions, including:
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`git_config_int`::
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Parse the string to an integer, including unit factors. Dies on error;
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otherwise, returns the parsed result.
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`git_config_ulong`::
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Identical to `git_config_int`, but for unsigned longs.
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`git_config_bool`::
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Parse a string into a boolean value, respecting keywords like "true" and
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"false". Integer values are converted into true/false values (when they
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are non-zero or zero, respectively). Other values cause a die(). If
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parsing is successful, the return value is the result.
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`git_config_bool_or_int`::
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Same as `git_config_bool`, except that integers are returned as-is, and
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an `is_bool` flag is unset.
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`git_parse_maybe_bool`::
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Same as `git_config_bool`, except that it returns -1 on error rather
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than dying.
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`git_config_string`::
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Allocates and copies the value string into the `dest` parameter; if no
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string is given, prints an error message and returns -1.
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`git_config_pathname`::
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Similar to `git_config_string`, but expands `~` or `~user` into the
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user's home directory when found at the beginning of the path.
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Include Directives
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------------------
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By default, the config parser does not respect include directives.
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However, a caller can use the special `git_config_include` wrapper
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callback to support them. To do so, you simply wrap your "real" callback
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function and data pointer in a `struct config_include_data`, and pass
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the wrapper to the regular config-reading functions. For example:
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-------------------------------------------
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int read_file_with_include(const char *file, config_fn_t fn, void *data)
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{
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struct config_include_data inc = CONFIG_INCLUDE_INIT;
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inc.fn = fn;
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inc.data = data;
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return git_config_from_file(git_config_include, file, &inc);
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}
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-------------------------------------------
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`git_config` respects includes automatically. The lower-level
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`git_config_from_file` does not.
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Custom Configsets
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-----------------
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A `config_set` can be used to construct an in-memory cache for
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config-like files that the caller specifies (i.e., files like `.gitmodules`,
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`~/.gitconfig` etc.). For example,
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----------------------------------------
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struct config_set gm_config;
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git_configset_init(&gm_config);
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int b;
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/* we add config files to the config_set */
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git_configset_add_file(&gm_config, ".gitmodules");
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git_configset_add_file(&gm_config, ".gitmodules_alt");
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if (!git_configset_get_bool(gm_config, "submodule.frotz.ignore", &b)) {
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/* hack hack hack */
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}
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/* when we are done with the configset */
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git_configset_clear(&gm_config);
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----------------------------------------
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Configset API provides functions for the above mentioned work flow, including:
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`void git_configset_init(struct config_set *cs)`::
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Initializes the config_set `cs`.
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`int git_configset_add_file(struct config_set *cs, const char *filename)`::
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Parses the file and adds the variable-value pairs to the `config_set`,
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dies if there is an error in parsing the file. Returns 0 on success, or
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-1 if the file does not exist or is inaccessible. The user has to decide
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if he wants to free the incomplete configset or continue using it when
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the function returns -1.
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`int git_configset_get_value(struct config_set *cs, const char *key, const char **value)`::
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Finds the highest-priority value for the configuration variable `key`
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and config set `cs`, stores the pointer to it in `value` and returns 0.
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When the configuration variable `key` is not found, returns 1 without
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touching `value`. The caller should not free or modify `value`, as it
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is owned by the cache.
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`const struct string_list *git_configset_get_value_multi(struct config_set *cs, const char *key)`::
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Finds and returns the value list, sorted in order of increasing priority
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for the configuration variable `key` and config set `cs`. When the
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configuration variable `key` is not found, returns NULL. The caller
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should not free or modify the returned pointer, as it is owned by the cache.
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`void git_configset_clear(struct config_set *cs)`::
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Clears `config_set` structure, removes all saved variable-value pairs.
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In addition to above functions, the `config_set` API provides type specific
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functions in the vein of `git_config_get_int` and family but with an extra
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parameter, pointer to struct `config_set`.
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They all behave similarly to the `git_config_get*()` family described in
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"Querying For Specific Variables" above.
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Writing Config Files
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--------------------
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Git gives multiple entry points in the Config API to write config values to
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files namely `git_config_set_in_file` and `git_config_set`, which write to
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a specific config file or to `.git/config` respectively. They both take a
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key/value pair as parameter.
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In the end they both call `git_config_set_multivar_in_file` which takes four
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parameters:
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- the name of the file, as a string, to which key/value pairs will be written.
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- the name of key, as a string. This is in canonical "flat" form: the section,
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subsection, and variable segments will be separated by dots, and the section
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and variable segments will be all lowercase.
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E.g., `core.ignorecase`, `diff.SomeType.textconv`.
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- the value of the variable, as a string. If value is equal to NULL, it will
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remove the matching key from the config file.
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- the value regex, as a string. It will disregard key/value pairs where value
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does not match.
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- a multi_replace value, as an int. If value is equal to zero, nothing or only
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one matching key/value is replaced, else all matching key/values (regardless
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how many) are removed, before the new pair is written.
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It returns 0 on success.
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Also, there are functions `git_config_rename_section` and
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`git_config_rename_section_in_file` with parameters `old_name` and `new_name`
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for renaming or removing sections in the config files. If NULL is passed
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through `new_name` parameter, the section will be removed from the config file.
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