Expand environment variables used in stowrc, as requested in
https://savannah.gnu.org/bugs/?41826
This is achieved by creating a new function expand_environment() that
replaces any substring of the form '$VAR' or '${VAR}' with contents of
environment variable $VAR. Literal '$' can be given by '\$'.
N.B. The function is only applied to the --target and --dir options,
and only for options specified in .stowrc; cli options are left
untouched.
Undefined variables are expanded to the empty string, as they would be
in normal shell parameter expansion.
Unit tests added accordingly:
- Test expand_environment():
* Expand $HOME
* Expand ${HOME}
* Expand ${WITH SPACE}
* Expand '\$HOME'. Expected is '$HOME'
* Expand ${UNDEFINED}. Expected is ''.
- Test that it's applied to the correct options.
- Test that CLI options are not expanded.
- The `sanitize_path_options` functions remove all trailing
and leading spaces. So any valid directory like ` 123`,
`123 ` can not be used
- Also if there are two directories ` 123` and `123`, and if
user pick the ` 123` as option to `-d` or `-t`, then stow pick
directory `123` as the argument instead of ` 123` as user want.
```
STOW_DIR=. stow -n -v3 -t \ 123 456
stow dir is /tmp/test
stow dir path relative to target 123 is ..
cwd now 123
cwd restored to /tmp/test
cwd now 123
Planning stow of package 456...
Stowing contents of ../456 (cwd=/tmp/test/123)
Planning stow of package 456... done
cwd restored to /tmp/test
WARNING: in simulation mode so not modifying filesystem.
```
- This commit remove the check in `sanitize_path_options` function,
and now stow can work with those directories. There have been a check
for valid directory, so we are safe.
