This issue covers implementing "internal" style (no shell expansion) aliases gh alias set <alias name> <expansion>.

Valid invocations

• gh alias set co pr checkout
• gh alias set co "pr checkout"

Expected outputs

Bad command:

$ gh alias set co pa checkout
X No such command: pa. Not saving alias.

Already in use:

$ gh alias set co pr checkout
X "co" alias is already in use as "pr checkout"

Success:

$ gh alias set co pr checkout
:check: "gh co" now expands to "gh pr checkout"