diff-find-source-location

diff-find-source-location is a compiled Lisp function in `diff-mode.el'.

(diff-find-source-location &optional OTHER-FILE REVERSE NOPROMPT)

Find out (BUF LINE-OFFSET POS SRC DST SWITCHED).
BUF is the buffer corresponding to the source file.
LINE-OFFSET is the offset between the expected and actual positions
of the text of the hunk or nil if the text was not found.
POS is a pair (BEG . END) indicating the position of the text in the buffer.
SRC and DST are the two variants of text as returned by `diff-hunk-text'.
SRC is the variant that was found in the buffer.
SWITCHED is non-nil if the patch is already applied.
NOPROMPT, if non-nil, means not to prompt the user.