Diagnostics should not include absolute paths

[evmar]

TypeScript Version: 3.1.0-dev.20180717, older verisons too

Search Terms: absolute path diagnostics

Code

// foo.ts
export {};
// bar.ts
import {nosuch} from './foo';

Expected behavior:
Error message about nosuch that mentions paths relative to the project.

Actual behavior:
Error message includes absolute path:

$ tsc
bar.ts:1:9 - error TS2305: Module '"/usr/local/google/home/evanm/t/foo"' has no exported member 'nosuch'.

1 import {nosuch} from './foo';
          ~~~~~~

This matters because:

• it's confusing and inconsistent with other error messages
• we don't want to include private paths in error messages
• if the editor services is running in the cloud or whatever then it references bogus paths

[mhegazy]

Internally a module is represented by its full name. i see how this is not desirable in error messages.. we will have to audit all places where we use symbolToString on a module symbol and ensure we show a module specifier that users can understand without being overly verbose. one option is to have a name relative to the current module. another is to make it relative to the current directory (on the command line).

[mhegazy]

//CC @DanielRosenwasser and @weswigham

[evmar]

I would expect it to be relative to baseUrl (?) like the paths printed in the front of diagnostic messages.