Fix nix help shell by properly handling command aliases
#13496
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Previously, `nix help shell` failed with "Nix has no subcommand 'shell'" despite `nix shell --help` working correctly. This happened because the `shell` command is actually an alias for `env shell`, and the help system wasn't resolving aliases when looking up documentation. This patch modifies the `showHelp` function to check for and resolve aliases before generating the manpage name, ensuring that shorthand commands like `shell` get proper help documentation. Closes: NixOS#13431
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…3496 Fix `nix help shell` by properly handling command aliases (backport #13496)
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…3496 Fix `nix help shell` by properly handling command aliases (backport #13496)
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Fix
nix help shellby properly handling command aliasesCloses: #13431
Problem
The
nix help shellcommand incorrectly fails withNix has no subcommand 'shell'despitenix shell --helpworking correctly. This happens becauseshellis actually an alias forenv shell, and the help system wasn't resolving these aliases when looking up documentation.This creates a confusing user experience where the shell command both exists and doesn't exist depending on how users try to access its documentation.
Solution
This PR modifies the
showHelpfunction insrc/nix/main.ccto check for and resolve aliases before generating the manpage name. When a user requests help for an aliased command likeshell, the system now correctly looks up the documentation for the actual command (env shell).The implementation is straightforward - it adds a few lines to the
showHelpfunction to check if the requested subcommand matches any aliases in thetoplevel.aliasesmap, and if so, replaces the subcommand with the actual command path before generating the manpage name.