There are some places in the systemd which are use the same pattern:
fd_cloexec(STDIN_FILENO, false);
fd_cloexec(STDOUT_FILENO, false);
fd_cloexec(STDERR_FILENO, false);
to unset CLOEXEC for standard file descriptors. This patch introduces
the stdio_unset_cloexec() function to hide this and make code cleaner.
In standard linux parlance, "hidden" usually means that the file name starts
with ".", and nothing else. Rename the function to convey what the function does
better to casual readers.
Stop exposing hidden_file_allow_backup which is rather ugly and rewrite
hidden_file to extract the suffix first. Note that hidden_file_allow_backup
excluded files with "~" at the end, which is quite confusing. Let's get
rid of it before it gets used in the wrong place.
This should allow tools like rkt to pre-mount read-only subtrees in the OS
tree, without breaking the patching code.
Note that the code will still fail, if the top-level directory is already
read-only.