feat: Implement `azdo pipelines variable delete` command

[tmeckel]

This issue tracks the implementation of the azdo pipelines variable delete command.

Command Description

Delete a variable from a pipeline definition. The Azure CLI obtains the definition, removes the variable from its dictionary, and updates the definition (source). azdo should provide confirmation prompts, fix the Azure CLI’s name/id lookup bug, and offer consistent output.

Important REST constraints:

• This command is implemented via Build Definitions: GET the definition, mutate its variables map, then PUT the updated definition.
• Definitions - Update requires the request body revision to match the current definition revision (GET → modify → PUT).
• Azure DevOps REST never returns secret variable values; this command must not attempt to display them (delete should not print values).

azdo Command Signature

azdo pipelines variable delete [ORGANIZATION/]PROJECT/PIPELINE_ID_OR_NAME --name VARIABLE_NAME [--yes]

Behavior

• Resolve scope and pipeline ID (when only a name is provided, look up the definition by name—note that the Azure CLI mistakenly passes the variable name instead; correct this in azdo).
• Start progress indicator, fetch definition, and locate the variable case-insensitively.
• Prompt for confirmation unless --yes is set (Delete variable '' from pipeline ''?). Return util.ErrCancel if declined.
• Remove the variable, update the definition (preserving the server’s revision requirement), stop progress.
• Output:
  • If stdout is connected to a TTY: print Variable deleted..
  • If stdout is not a TTY: emit no output on success.
• Debug logging for pipeline resolution, prompt decisions, and variable removal.

Implementation Notes (filled checklist)

• Implement command: internal/cmd/pipelines/variable/delete/delete.go (type opts struct, NewCmd(ctx), run(ctx, opts)).
• Wire command: internal/cmd/pipelines/variable/variable.go must AddCommand(delete.NewCmd(ctx)) and be reachable from azdo pipelines.
• Parse scope: util.ParseProjectTargetWithDefaultOrganization(ctx, targetArg) for [ORGANIZATION/]PROJECT/PIPELINE_ID_OR_NAME; wrap parse errors with util.FlagErrorWrap.
• Clients:
  • Build: ctx.ClientFactory().Build(ctx.Context(), scope.Organization) using Definitions - Get and Definitions - Update.
  • Prompter only for confirmation prompt (unless --yes).
• Resolution algorithm:
  • If PIPELINE_ID_OR_NAME is numeric, treat as definitionId.
  • Otherwise resolve by name via Definitions - List (handle multiple matches explicitly).
• Update algorithm:
  • GET definition by id.
  • Delete variable key (case-insensitive).
  • PUT updated definition, ensuring revision matches the GET result.
• Output:
  • If stdout is a TTY: print Variable deleted..
  • If stdout is not a TTY: no output on success.
• Tests:
  • Add unit tests at internal/cmd/pipelines/variable/delete/delete_test.go.
  • Hermetic mocks: Build client + prompter.
  • Table-driven cases: delete by id with --yes, delete by name resolution, missing variable, prompt decline -> util.ErrCancel, stdout TTY vs non-TTY output behavior.

Command Wiring

• Implement the command in internal/cmd/pipelines/variable/delete/delete.go exposing NewCmd(ctx util.CmdContext) *cobra.Command.
• Register it from the parent internal/cmd/pipelines/variable/variable.go so the CLI hierarchy includes azdo pipelines variable delete.

SDK / Client Requirements

• Requires the Build client (ClientFactory().Build(...)) to retrieve and update pipeline definitions. Confirm that the client is exposed; if not, follow "Handling Missing Azure DevOps SDK Clients" in AGENTS.md (extend ClientFactory, run go mod tidy and go mod vendor, update scripts/generate_mocks.sh, and implement the factory method).

References

• Azure CLI implementation: pipeline_variable_delete