Enable templating on inheritConfigFileName

[castielwaverly]

Tell us more.

Currently this is supported in inheritConfigRepoName, which lets you do fancy stuff like define onboarding configs per organization under {{ myOrg }}/renovate-config.

One thing this doesn't let you do, however, is have a single "renovate control panel" repo to manage all repos across all orgs. If you could template inheritConfigFileName, you would be able to place these files in nested folders in a single repo, making management more streamlined.

For example, instead of creating N {{ orgN }}/renovate-config repos with each of their own onboarding configs, you would instead create N {{ orgN }}/org-inherited-config.json files in your one repo and specify:

"inheritConfig": true,
"inheritConfigRepoName": "admin-org/my-renovate-control-panel",
"inheritConfigFileName": "{{parentOrg}}/org-inherited-config.json"

In general, it's much easier managing multiple files in one repo than the "same" files across many repos, though I wonder if this was left out intentionally to prevent some clever abuse I can't think of at the moment.

In any case, I did take a look at the code...

The unparsed template for inheritConfigRepoName is parsed here:

renovate/lib/workers/repository/init/inherited.ts

Lines 48 to 52 in 6f577f0

	const inheritConfigRepoName = template.compile(
	config.inheritConfigRepoName,
	templateConfig,
	false,
	);

Which then is used to get the raw config file here:

renovate/lib/workers/repository/init/inherited.ts

Lines 62 to 65 in 6f577f0

	configFileRaw = await platform.getRawFile(
	config.inheritConfigFileName,
	inheritConfigRepoName,
	);

There may be additional complexities elsewhere, but it does seem like inheritConfigFileName can be "elevated" to a templated configuration with

   const inheritConfigRepoName = template.compile(
     config.inheritConfigRepoName,
     templateConfig,
     false,
   );
+  const inheritConfigFileName = template.compile(
+    config.inheritConfigFileName,
+    templateConfig,
+   false,
+  );

  ...

     configFileRaw = await platform.getRawFile(
-      config.inheritConfigFileName,
+      inheritConfigFileName,
       inheritConfigRepoName,
     );

^{...and a few more search and replaces, of course}

It does feel like the quality of life improvement is about on par with the complexity of the required change to achieve said improvement. Thoughts?

[RahulGautamSingh]

PR welcome