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 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. The name of the attribute can be retrieved by calling git_attr_name().
struct git_attr_check: This structure represents a set of attributes to check in a call to git_check_attr() function, and receives the results.

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.

Querying Specific Attributes

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_check_attr() 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.

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");
        check[1].attr = git_attr("ident");
}

Call git_check_attr() with the prepared array of struct git_attr_check:

        const char *path;

        setup_check();
        git_check_attr(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 ...) {
                ...
        }

Querying All Attributes

To get the values of all attributes associated with a file:

Call git_all_attrs(), which returns an array of git_attr_check structures.
Iterate over the git_attr_check array to examine the attribute names and values. The name of the attribute described by a git_attr_check object can be retrieved via git_attr_name(check[i].attr). (Please note that no items will be returned for unset attributes, so ATTR_UNSET() will return false for all returned git_array_check objects.)
Free the git_array_check array.