Fixes#80.
Disable by default the symlinks resolution, making a symlink and its
target 2 different entries in the database. Adds the
_ZO_RESOLVE_SYMLINKS env variable to re-enable it.
Example:
/tmp/foo-target is a directory
/tmp/foo symlinks to /tmp/foo-target
With _ZO_RESOLVE_SYMLINKS=1, `z add /tmp/foo` adds `/tmp/foo-target` in the database.
With _ZO_RESOLVE_SYMLINKS=0 or unset, `z add /tmp/foo` adds `/tmp/foo` in the database.
Add POSIX shell support
Any users of a shell that adheres to the POSIX standard should now be
supported. Shells that were tested while this feature was in development
include `mrsh`, `dash`, busybox `ash`, and `bash --posix`.
The hook works by defining a `_zoxide_hook` function and adding it to
the shell's `PS1` (causing it to be evaluated every time the prompt is
redrawn).
The PWD hook has been removed, because it is impossible to implement in
a POSIX-compliant and satisfactory way.
* Migrate errors from failure to anyhow
* Migrate argument parsing from clap to structopt
* Empty z command now goes to $HOME
* DB updates are now atomic and isolated
