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authorJunio C Hamano <gitster@pobox.com>2007-11-25 07:48:04 (GMT)
committerJunio C Hamano <gitster@pobox.com>2007-12-15 06:29:38 (GMT)
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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>
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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)