Bazel: Document runfiles

[pauldraper]

Description of the problem / feature request:

Document runfiles resolution.

Feature requests: what underlying problem are you trying to solve with this feature?

I need to know how to access data files at runtime.

Specifically in the following scenarios:

1. During bazel build action
2. During bazel test
3. During bazel run
4. During direct executable invocation

And

1. When invoked directly.
2. When invoked indirectly as a data-dependency of another executable.

And

1. On Linux/Mac (symlink tree and manifest)
2. On Windows (manifest)
3. With sandboxing (symlink tree)

Have you found anything relevant by searching the web?

https://docs.bazel.build/versions/master/skylark/rules.html#runfiles

http://jayconrod.com/posts/108/writing-bazel-rules--data-and-runfiles

https://github.com/bazelbuild/bazel/issues/4460

https://docs.google.com/document/d/e/2PACX-1vSDIrFnFvEYhKsCMdGdD40wZRBX3m3aZ5HhVj4CtHPmiXKDCxioTUbYsDydjKtFDAzER5eg7OjJWs3V/pub

Any other information, logs, or outputs that you want to share?

Documentation should include:

1. The generic resolution algorithm
2. Instructions for using language-specific libraries implementing the algorithm
3. Ideally some brief explanation/motivation why this is so dang hard.

[pauldraper]

Bump

[pauldraper]

Related proposal: https://docs.google.com/document/d/10aW-UrKPjGkxQGGEblGba6LAWupqbssx-bjywVCmJvY/edit#heading=h.xgjl2srtytjt

[pauldraper]

Possible duplicate of #4054

[meisterT]

Cc @laszlocsomor @philwo

[laszlocsomor]

Paul is right.
I'll work on it.

[meisterT]

Thanks Laszlo!

[laszlocsomor]

Progress: https://github.com/laszlocsomor/bazel/commit/ba821c81092a768c36d6bd373492e8d5088151a1

I have to work on something else now.

[pauldraper]

@laszlocsomor that's good stuff; I hope you will have time for more.

[pauldraper]

I have found additional documentation in the recent and very informative Bazel guide by Lukacs.

https://docs.google.com/document/d/1wzjTCuqXNKBlEEHCVw17j7kil2qx04sBsMZCTZzOJj0/edit#heading=h.rpcqrjsxgnpk

[laszlocsomor]

Sorry about my recent silence. I have not forgotten about this issue, and I intend to work more on it this week.

[laszlocsomor]

Finally found some time -- here's more update, starting to dig into the messy details.