Commit Briefs
Avoid out of bounds access if path is "/".
From Martin <openbsd () academicsolutions ! ch> with tweaks by me. ok stsp
make 'got commit' look up EDITOR in PATH
The previous code only worked if EDITOR contained an absolute path.
got_error_from_errno -> got_error_prefix_errno
also add got_error_prefix_errno2 and got_error_prefix_errno3 which should hopefully all be merged into a single function with variadic args (but can't alloc mem)