Resolve relative repo paths from config file directory (#1443)
* fix: resolve relative repo paths from config file directory
Relative paths like `../hook-repo` in `.pre-commit-config.yaml` were
being resolved against the process's current working directory instead
of the directory containing the config file. This broke configs in
subprojects that used relative paths to hook repositories.
The fix resolves relative repo paths in `Project::from_config_file`
right after loading the config, using the config file's parent
directory as the base.
Fixes #1065
* Minor tweaks
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Co-authored-by: Jo <10510431+j178@users.noreply.github.com>