Allow querying all attributes on a file

Add a function, git_all_attrs(), that reports on all attributes that
are set on a path.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/technical/api-gitattributes.txt

@@ -22,19 +22,6 @@ Data Structure
 	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
 ----------------
 
@@ -58,6 +45,19 @@ 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_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.
+
+
 Example
 -------
 
@@ -109,4 +109,20 @@ static void setup_check(void)
 	}
 ------------
 
-(JC)
+
+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.