The little known beauty of .ensure files

Ever broken the build?

Everyone who uses a revision control system has, at some point, accidentally committed a file that should never have been committed. For example, a ".dll" or a dreaded ".suo" file.

To save us from this entire category of problem, the ".ignore" concept was created, and implemented as a built-in feature of many revision control systems (for example ".gitignore" and ".hgignore")

Similarly: everyone has, at some time, forgotten to "commit" a file that other parts of the code relied upon. Thus, the build has been broken, time and time again. Throughout the world, builds are breaking at this very moment, for the lack of some file that could've so easily been committed.

There is a widespread but little known feature, as simple as the ".ignore" file, that addresses this problem.

If you're not familiar with it, let me tell you about the ".ensure" file.

A ".ensure" file informs the repository of a few basic standards of file hygiene that must be achieved before a push can be issued.

Much like a ".ignore" file, You can copy a ".ensure" from some one else's similar project into your own, and everything will just work.

You can copy a ".ensure" from some one else's similar project into your own, and everything will just work.

For example, if someone else has written a C# based project, where the ".ensure" file says, in effect:

"If there is a '.sln' file in the repo, each referenced project file must also be part of the repo 
"If there is a '.csproj' file in the repo, each referenced file or resource must also be part of the repo

...then you can copy their ".ensure" file into your own C# project, and you will be protected against so many entirely predictable build breakages.

Admittedly, the syntax of a ".ensure" file is a little baroque, cramming up to four "selection" DSL into the one handy file format (regex, xpath, jsonquery and globs).

But most people never write them: they simply copy them from place to place. (Copying files comes naturally to developers at every rung of the ladder.)

And testing the effectiveness of a given ".ensure" file is very easy (you just try to break the build with a missing file). So the community easily converged on a working set of files for any given project type.

The only problem that anyone has with ".ensure" files, is that they are something Leon simply dreamed up, five minutes ago, while doing the dishes. Implementations are yet to exist.

I for one say: go for it.

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