https://issues.dlang.org/show_bug.cgi?id=13704

          Issue ID: 13704
           Summary: Confusing error message when passing the same on the
                    command line twice
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Windows
            Status: NEW
          Keywords: diagnostic
          Severity: enhancement
          Priority: P3
         Component: DMD
          Assignee: nobody@puremagic.com
          Reporter: r.sagitario@gmx.de

This happens to me sometimes when merging branches for druntime or phobos:

>dmd src\gc\config.d src\gc\config.d
Error: module gc.config from file src\gc\config.d must be imported with 'import gc.config;'

bacause the command line is too long to spot duplicates.

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