Add a feature for overwriting the whole output file

[imgrant]

This PR adds an out option, consumeWholeFile (boolean, default: false), which can be used with plain output type files to simply always overwrite the whole file with the new version number, rather that doing a search-and-replace operation with the existing contents (the current behaviour).

This can be useful when the output file cannot be guaranteed to be up-to-date (i.e. contain the matching latest version). It also goes some way to matching the behaviour of structured output files such as JSON — e.g. the new version is always written to the { "version" } field in package.json, regardless of whether the existing { "version": "<value>" } matches that latest version or not.

One caveat is that version number prefixes are not retained, e.g. if plain output file VERSION contains v1.0.0, a patch release would replace it with 1.0.1 (no v prefix). This replicates the behaviour when the output file does not exist at all — current behaviour there is that bumper writes the new version number to the file, sans prefix.

Fixes #31

[webpro]

🚀 This pull request is included in v5.1.0. See Release 5.1.0 for release notes.

[webpro]

Thanks @imgrant! Even though there's a simple(r) solution to writing the version to a file, I agree it's nice to keep config together.

[imgrant]

Excellent, glad to see it merged. Thanks!