Turns out we don't need sed to process the output of gcc -MD. We can just
do this:
read DEPS <filename.deps
The 'read' command in sh actually handles backslashes correctly, so we don't
have to sed them out after all. And then a simple ${DEPS#*:} removes the
"target:" prefix from the dependency line, and we're done!
We have to go through some pretty scary gyrations to extract this
information from git, but it can be done. This works with both tarballs
generated by 'git archive', or with your local git repo.
(Requested by 'David' on the mailing list.)