cmd: fallback to parsing getent passwd output when $SHELL is not set

[Rolv-Apneseth]

As suggested in #1615, this PR just adds a fallback if $SHELL is not set for whatever reason.

Not very comfortable with Go, but hopefully the code is alright. Happy to make any changes anyway. And let me know if you want some tests added, I just wasn't sure entirely where to add that.

[gemini-code-assist]

Summary of Changes

Hello @Rolv-Apneseth, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the application's ability to reliably determine the user's default shell. It addresses scenarios where the $SHELL environment variable might be unset by introducing a new utility function that attempts to read $SHELL and, if unsuccessful, gracefully falls back to parsing the output of the getent passwd command. This change ensures that core functionalities dependent on the user's shell can proceed without error, making the application more resilient to varied environment configurations.

Highlights

• Robust Shell Detection: Implemented a fallback mechanism to determine the user's default shell when the $SHELL environment variable is not set, improving application robustness.
• New Utility Function: Introduced a new getUserShell utility function in src/cmd/utils.go to encapsulate the logic for retrieving the shell, first checking $SHELL and then falling back to parsing getent passwd output.
• Refactored Shell Acquisition: Updated create.go, enter.go, and rootMigrationPath.go to utilize the new getUserShell function instead of directly relying on os.Getenv("SHELL").

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Changelog

• src/cmd/create.go
  • Replaced direct os.Getenv("SHELL") call with a call to the new getUserShell() function.
• src/cmd/enter.go
  • Replaced direct os.Getenv("SHELL") call with a call to the new getUserShell() function.
• src/cmd/rootMigrationPath.go
  • Replaced direct os.Getenv("SHELL") call with a call to the new getUserShell() function.
• src/cmd/utils.go
  • Added a new getUserShell() function that first checks the $SHELL environment variable.
  • Implemented fallback logic within getUserShell() to execute and parse /bin/getent passwd output if $SHELL is empty.
  • Added error handling for getent command execution and output parsing.
  • Ensured the $SHELL environment variable is set for subsequent operations if determined via getent.

Activity

• The author initiated this pull request to address an issue identified in failed to get the current user's default shell #1615, providing an initial implementation for a shell fallback mechanism.
• The author expressed openness to feedback and making further changes, including adding tests if deemed necessary, indicating a collaborative approach to development.

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[gemini-code-assist]

Code Review

This pull request adds a fallback mechanism to determine the user's shell by parsing getent passwd output when the $SHELL environment variable is not set. This is a good improvement for robustness. The changes are applied consistently across the create, enter, and rootMigrationPath commands. My review includes a couple of suggestions for the new getUserShell function in src/cmd/utils.go to enhance its portability and robustness. Additionally, since you've mentioned being open to adding tests, it would be great to add unit tests for the new getUserShell function to cover both the successful paths and the error cases you're handling. This would improve the long-term maintainability of this new logic.

[softwarefactory-project-zuul]

Build succeeded.
https://softwarefactory-project.io/zuul/t/local/buildset/9ede5df2b2b848c1b6179380cab7f6f9

✔️ unit-test SUCCESS in 2m 10s
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