chore(deps): update dependency black to v24.4.1

Currently, `pass-git-helper` doesn't check if a password file exists before
running `pass`. This leads to authentication failures when the configured
password store entry (aka `target`) points to a directory instead of a file.

Example:

    $ tree -F .password-store
    .password-store/
    └── git/
        ├── github.com.gpg
        └── gitlab.com/
            ├── user1.gpg
            └── user2.gpg

If target is `git/gitlab.com`, `pass-git-helper` will get the following output
from `pass git/gitlab/com`:

    git/gitlab.com
    ├── user1
    └── user2

and will then use the first line (`git/gitlab/com`) as password.

This commit introduces the following changes:

1. To fix the problem described above, `pass-git-helper` first determines the
   `pass` password store directory as:

   - the value of `password_store_dir` if defined in `git_pass_mapping.ini` (and
     non-empty)
   - the value of the environment variable `PASSWORD_STORE_DIR` if defined (and
     non-empty)
   - the default: `~/.password-store`

   (the latter two correspond to the implementation of `pass`).
   `pass-git-helper` will then check if an actual `<target>.gpg` is present in
   the selected directory (to be clear: only one of the three alternative
   directories gets checked).

   The new checks implemented in `pass-git-helper` detect two different error
   cases:
   1. the scenario described above where `target` itself is a directory
   2. a (rather obscure) scenario where `<target>.gpg` is a directory

   In both cases, `pass-git-helper` will now exit with an error after presenting
   the user with a (hopefully) useful error message.

2. The value of `password_store_dir` in the ini file may now contain a leading
   `~` (*tilde*) which will get replaced by the users *HOME* (or, on Windows,
   *USERPROFILE*) directory. The change is documented in README.md.

3. New tests for 1. and 2.

Fixes #371

…ssword-file

feat: check if password file exists before running `pass`

# [1.5.0](v1.4.1...v1.5.0) (2024-04-25)

### Features

* check if password file exists before running `pass` ([b50ca3b](b50ca3b)), closes [#371](#371)