Installer: display info about shell config file if unable to write to it.

[MaddyGuthridge]

In particular, this displays information about the config file's:

• Owner
• Permissions
• Real path (if it is a symlink)

It then suggests that users may need to modify the file's permissions to grant $(whoami) write access.

Example outputs:

• .zshrc is owned by root:

=> Appending nvm source string to /home/maddy/.zshrc
install.sh: line 479: /home/maddy/.zshrc: Permission denied
=> Failed to add nvm source string to /home/maddy/.zshrc
=> Info about /home/maddy/.zshrc:
   Owner: root (you are maddy)
   Permissions: -rw-r--r--
=> You may need to modify the file owner or permissions to grant maddy
   write access.
=> Or, you can the following lines to the file yourself:

export NVM_DIR="$HOME/.nvm"
[ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"  # This loads nvm

• .zshrc is a symlink, and the target file does not have write permissions

=> Appending nvm source string to /home/maddy/.zshrc
install.sh: line 479: /home/maddy/.zshrc: Permission denied
=> Failed to add nvm source string to /home/maddy/.zshrc
=> Info about /home/maddy/.zshrc:
   Real path of /home/maddy/.zshrc: /home/maddy/.dotfiles/Configs/global/.zshrc
   Owner: maddy (you are maddy)
   Permissions: -r--r--r--
=> You may need to modify the file owner or permissions to grant maddy
   write access.
=> Or, you can the following lines to the file yourself:

export NVM_DIR="$HOME/.nvm"
[ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"  # This loads nvm

Testing

• I have tested this on NixOS 25.11, where it worked for the above cases, and for when there are no permission issues.
• I have tested this on MacOS 26.3, where it has also worked correctly.
• Should I write some integration tests for this? If so, can I get some info on how the testing works in this repo? Is it just a collection of shell scripts?

Additional notes

• This is my first contribution to this project! Yippee!
• I don't consider myself to be an expert at shell scripting, so I'd love any constructive criticism to improve my code style or safety (I don't wanna accidentally rimraf someone's home directory or something).
• As requested, this PR does not contain any AI-generated content, and is entirely my own work
• Resolves Install script: provide a nicer error if NVM cannot be added to the user's shell configuration due to permission issues #3788

[ljharb]

Thanks, this is great! Could we add some unit tests for nvm_profile_info?