Make intraline edit pairs relative.

Previously, the first parameter in the pair was the absolute offset.
Update the first item to mean the number of characters to skip until
the next edit.  That way, it makes it more obvious on the ordering
of elements and how the markup logic should be implemented.

Change-Id: I8c2f740466fbe07ec4e5c1d5bfff93a8299bcb29

Documentation/rest-api-changes.txt

diff --git a/Documentation/rest-api-changes.txt b/Documentation/rest-api-changes.txt
index daf0f7e..0169bff 100644
--- a/Documentation/rest-api-changes.txt
+++ b/Documentation/rest-api-changes.txt
@@ -2531,14 +2531,14 @@
 The `DiffIntralineInfo` entity contains information about intraline edits in a
 file.
 
-The information consists of a list of `<offset, length>` pairs.  The pairs are in
-ascending order and there is no overlap.  The offset is from the beginning of the
-related diff content lines, and the length is the number of characters that were
-edited.
+The information consists of a list of `<skip length, mark length>` pairs.  Where
+the skip length is the number of characters between between the end of the
+previous edit and the start of this edit. The mark length is the number of
+edited characters following the skip. The start of the edits is from the
+beginning of the related diff content lines.
 
-Note that the implied newline character is included at the end of each line when
-computing the offset and length, and thus it is possible for the edits to span
-newlines.
+Note that the implied newline character at the end of each line is include in
+the length calculation, and thus it is possible for the edits to span newlines.
 
 [[fetch-info]]
 FetchInfo