Hide test binaries behind a feature flag

[yusufraji]

split-patch now has two rust binaries used in tests. This number could increase in the future. And it is possible that the binaries are made available to any installs split-patch via cargo install.

This is discussed in #21 (comment)

Hiding test binaries under a feature flag could prevent them from being bundled with the default split-patch. Should also make the binary theoretically smaller.

[pflanze]

This is only a possibility if the alternatives don't work. I'd try to avoid complicating the project with features that have followup complications. Thus first test:

• if "cargo install split-patch" (and we haven't even published it yet) doesn't do the right thing of only installing the binary under src/bin/ (remember I haven't verified)
• Then, given that we want to document in the README that it should probably be "cargo install --locked split-patch" anyway, whether just also adding "--bin split-patch" is really so bad.
• Then, we could also move the test infrastructure binaries to a separate crate. This is likely better than the feature flag.

[pflanze]

Should also make the binary theoretically smaller

Each binary is compiled separately, so it will have no effect on the size of split-patch binary if that's what you meant.

[pflanze]

So I suggest to do in order:

1. Move main crate to a subdir, too (Move split-patch crate to a subdir, too #14)
2. Implement workspace (Configure workspaces #10)
3. Decide on license for the split-patch crate together (Add license to the split-patch crate #11), publish on crates.io
4. Test what cargo install does, decide what to do about it.

[yusufraji]

Should also make the binary theoretically smaller

Each binary is compiled separately, so it will have no effect on the size of split-patch binary if that's what you meant.

Yes, that's what I meant. It should be alright in that case.