Incomplete description of tsBuildInfoFile config default behavior

[henry-filosa]

It seems to me that the default description of https://www.typescriptlang.org/tsconfig#tsBuildInfoFile is incomplete. It simply says that the default outfile is .tsbuildinfo, but this PR lays out much more complex behavior:

• When tsconfig specifies compiler options incremental file with .tsbuildinfo extension is emitted.
• Composite projects indirectly specify incremental as true and its error to specify incremental as false in the composite project
• If project specifies tsBuildInfoFile options, it uses the path specified by that to write the build information.
• If project specifies out or outFile option, the outFileWithoutExtension.tsbuildinfo file is written next to output js file.
• If project specified outDir, config files base file name with extension as .tsbuildinfo is written in outDir
• Otherswise config files base file name with extension as .tsbuildinfo is written next to the config file

Highlights added by me. This means that my incremental build file is tsconfig.tsbuildinfo as we follow the common convention of tsconfig.json. While this behavior is not a huge deal, I think it's preferable to have it documented. As it stands I had to delve into a years old PR to figure out why the documented behavior didn't match my observed behavior.

[typescript-bot]

Hello! As per #2804, we are automatically closing all open issues. Please see #2804 for a description of what issues and PRs can be accepted going forward.