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git/Documentation/technical/api-gitattributes.txt
Junio C Hamano 530e741c72 Start preparing the API documents.
Most of them are still stubs, but the procedure to build the HTML
documentation, maintaining the index and installing the end product are
there.

I placed names of people who are likely to know the most about the topic
in the stub files, so that volunteers will know whom to ask questions as
needed.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2007-12-14 22:29:38 -08:00

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gitattributes API
=================
gitattributes mechanism gives a uniform way to associate various
attributes to set of paths.
Data Structure
--------------
`struct git_attr`::
An attribute is an opaque object that is identified by its name.
Pass the name and its length to `git_attr()` function to obtain
the object of this type. The internal representation of this
structure is of no interest to the calling programs.
`struct git_attr_check`::
This structure represents a set of attributes to check in a call
to `git_checkattr()` function, and receives the results.
Calling Sequence
----------------
* Prepare an array of `struct git_attr_check` to define the list of
attributes you would want to check. To populate this array, you would
need to define necessary attributes by calling `git_attr()` function.
* Call git_checkattr() to check the attributes for the path.
* Inspect `git_attr_check` structure to see how each of the attribute in
the array is defined for the path.
Attribute Values
----------------
An attribute for a path can be in one of four states: Set, Unset,
Unspecified or set to a string, and `.value` member of `struct
git_attr_check` records it. There are three macros to check these:
`ATTR_TRUE()`::
Returns true if the attribute is Set for the path.
`ATTR_FALSE()`::
Returns true if the attribute is Unset for the path.
`ATTR_UNSET()`::
Returns true if the attribute is Unspecified for the path.
If none of the above returns true, `.value` member points at a string
value of the attribute for the path.
Example
-------
To see how attributes "crlf" and "indent" are set for different paths.
. Prepare an array of `struct git_attr_check` with two elements (because
we are checking two attributes). Initialize their `attr` member with
pointers to `struct git_attr` obtained by calling `git_attr()`:
------------
static struct git_attr_check check[2];
static void setup_check(void)
{
if (check[0].attr)
return; /* already done */
check[0].attr = git_attr("crlf", 4);
check[1].attr = git_attr("ident", 5);
}
------------
. Call `git_checkattr()` with the prepared array of `struct git_attr_check`:
------------
const char *path;
setup_check();
git_checkattr(path, ARRAY_SIZE(check), check);
------------
. Act on `.value` member of the result, left in `check[]`:
------------
const char *value = check[0].value;
if (ATTR_TRUE(value)) {
The attribute is Set, by listing only the name of the
attribute in the gitattributes file for the path.
} else if (ATTR_FALSE(value)) {
The attribute is Unset, by listing the name of the
attribute prefixed with a dash - for the path.
} else if (ATTR_UNSET(value)) {
The attribute is not set nor unset for the path.
} else if (!strcmp(value, "input")) {
If none of ATTR_TRUE(), ATTR_FALSE(), or ATTR_UNSET() is
true, the value is a string set in the gitattributes
file for the path by saying "attr=value".
} else if (... other check using value as string ...) {
...
}
------------
(JC)