fix: clean should preserve and remove files from sourceRoots

[lqiu96]

Fixes: #1860

[codecov]

Codecov Report

❌ Patch coverage is 87.80488% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.08%. Comparing base (89524de) to head (148e3bd).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/librarian/command.go	87.80%	8 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1950      +/-   ##
==========================================
+ Coverage   82.01%   82.08%   +0.06%     
==========================================
  Files          83       83              
  Lines        8793     8825      +32     
==========================================
+ Hits         7212     7244      +32     
- Misses       1231     1232       +1     
+ Partials      350      349       -1     

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[suztomo]

Sorry! My commit bf68599 made the conflict here.

[lqiu96]

Sorry! My commit bf68599 made the conflict here.

No worries. I was able to resolve the merge conflicts. Thanks for the heads up :)

[JoeWang1127]

Generally looks good, left comments on testing coverage.

[lqiu96]

Error:

--- FAIL: TestGoGenerate (1.34s)
    doc_generate_test.go:29: 
    doc_generate_test.go:30: 
    doc_generate_test.go:36: go generate produced a diff, please run `go generate ./...` and commit the changes
    doc_generate_test.go:39: diff:
        diff --git a/internal/librarian/doc.go b/internal/librarian/doc.go
        index b40b00c..18b7e0f 100644
        --- a/internal/librarian/doc.go
        +++ b/internal/librarian/doc.go
        @@ -24,10 +24,9 @@ Usage:
         	librarian <command> [arguments]
         
         The commands are:
        -  generate                   onboards and generates client library code
        -  release                    manages releases of libraries.
        -  version                    prints the version information
        -
         
        +	generate                   onboards and generates client library code
        +	release                    manages releases of libraries.
        +	version                    prints the version information
         */
         package librarian