feat(appsignal-cli): add plugin for AppSignal (#14038)

plugins/appsignal-cli/README.md

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+# AppSignal CLI plugin
+
+This plugin adds aliases, guard rails and completion for the
+[AppSignal CLI](https://docs.appsignal.com/cli).
+
+To use it, add `appsignal-cli` to the plugins array in your zshrc file:
+
+```zsh
+plugins=(... appsignal-cli)
+```
+
+## Requirements
+
+[AppSignal CLI](https://docs.appsignal.com/cli) 2.1 or newer, installed and on
+your `PATH`. The plugin does nothing if it is not:
+
+```zsh
+brew install appsignal/appsignal-cli/appsignal-cli
+# or
+curl -sSL https://github.com/appsignal/appsignal-cli/releases/latest/download/install.sh | sudo sh
+```
+
+Most commands need `appsignal-cli auth login` first.
+
+## Aliases
+
+| Alias   | Command                        | Description                        |
+| :------ | :----------------------------- | :--------------------------------- |
+| `asig`  | `appsignal-cli`                | The AppSignal CLI itself           |
+| `aslog` | `appsignal-cli logs tail`      | Stream log lines as they arrive    |
+| `asinc` | `appsignal-cli incidents list` | List incidents for an application  |
+
+`aslog` and `asinc` complete like the commands they stand in for, so
+`aslog --<TAB>` offers the flags of `appsignal-cli logs tail`.
+
+## Functions
+
+| Function        | Description                                                        |
+| :-------------- | :----------------------------------------------------------------- |
+| `appsignal-cli` | Wraps the CLI to confirm before irreversible commands. See Settings |
+
+## Completion
+
+Every command completes with a description of what it does, at every level, and
+so do their flags and allowed values: incident states and severities, sort
+orders, log severities, trigger fields and comparison operators, output formats
+and skill targets. `samples` and `sample` complete like `traces`, as they do in
+the CLI itself.
+
+`--org` completes offline from the `org` key of your project's
+`.appsignal.toml` and of the global config.
+
+The AppSignal CLI ships no completion generator of its own, so `_appsignal-cli`
+is written from its command definitions and kept in this repository. It targets
+AppSignal CLI 2.1.x.
+
+## Settings
+
+Set these with `zstyle` in your zshrc, before Oh My Zsh is sourced.
+
+### Confirming destructive commands
+
+```zsh
+zstyle ':omz:plugins:appsignal-cli' confirm-destructive no
+```
+
+By default the plugin asks for confirmation before four operations that the CLI
+itself performs without a prompt:
+
+- `appsignal-cli logs metrics delete`
+- `appsignal-cli logs triggers delete`
+- `appsignal-cli triggers archive`, which also closes the trigger's alerts and
+  incidents
+- `appsignal-cli incidents update --state CLOSED` when it names more than one
+  incident, since that flag accepts a comma-separated list
+
+Nothing else is intercepted, and the prompt is skipped when stdin is not a
+terminal, so scripts, pipelines and CI are unaffected. Set the style to `no` to
+turn the prompt off entirely, or run `command appsignal-cli` for a single
+invocation.
+
+### Completing applications
+
+```zsh
+zstyle ':omz:plugins:appsignal-cli' dynamic-app-completion yes
+```
+
+Off by default. When enabled, `--app`, `--app-id` and `--environment` are
+completed from `appsignal-cli apps list --output json`, showing each
+application's name and environment next to its ID instead of making you copy
+IDs by hand. It is opt-in because it runs the CLI and makes a network call when
+you press <kbd>Tab</kbd>, and because it needs you to be authenticated. Results
+are cached for five minutes.
+
+### Disabling the aliases
+
+This works for every Oh My Zsh plugin:
+
+```zsh
+zstyle ':omz:plugins:appsignal-cli' aliases no
+```
+
+## Caveats
+
+- `appsignal-cli` and the AppSignal Ruby gem's `appsignal` command are different
+  tools. The gem's command installs and diagnoses the agent inside your app;
+  this one queries your data. The plugin deliberately leaves `appsignal` alone,
+  so it keeps working in projects that use the gem.
+- `appsignal-cli` is a shell function here. Run `command appsignal-cli` to reach
+  the binary directly.
+- Most commands need exactly one of `--app-id` or `--app`. `--environment` only
+  narrows `--app`; it does nothing next to `--app-id`.
+- `appsignal-cli project init` writes `.appsignal.toml`, and `auth login` then
+  stores OAuth tokens in it. Do not commit that file.
+- `incidents delete-note`, `auth logout` and the `--clear-*` flags of
+  `logs metrics update` and `logs triggers update` are destructive too, but are
+  not prompted for: each affects a single note, login or field.
+- `triggers create` and `triggers update` have their own `--format`, for the
+  format of the metric value. Everywhere else `--format` is a synonym for
+  `--output`.
+- The CLI sends usage telemetry by default. `APPSIGNAL_CLI_TELEMETRY=0` turns it
+  off, and `APPSIGNAL_CLI_DEBUG=1` shows internal errors.

plugins/appsignal-cli/appsignal-cli.plugin.zsh

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+# AppSignal CLI: completion, aliases and guard rails.
+# https://docs.appsignal.com/cli
+
+if (( ! $+commands[appsignal-cli] )); then
+  return
+fi
+
+# Does this invocation need confirming? Sets REPLY to the reason.
+#
+# The command path is collected from the leading bare words. Only the global
+# flags may precede a subcommand, so the first other flag ends the path: that
+# way an option value such as `--app "My App"` is never mistaken for one.
+function _appsignal_cli_is_destructive() {
+  zstyle -T ':omz:plugins:appsignal-cli' confirm-destructive || return 1
+
+  # Nobody to answer: CI and pipelines are unaffected.
+  [[ -t 0 ]] || return 1
+
+  local -a args=("$@") path numbers
+  local arg state=""
+  integer i=1 n=$# path_done=0
+
+  while (( i <= n )); do
+    arg="$args[i]"
+    case "$arg" in
+      --) break ;;
+      --state=*) state="${arg#--state=}"; path_done=1 ;;
+      --state) state="$args[i+1]"; (( i++ )); path_done=1 ;;
+      --number=*) numbers+=(${(s:,:)${arg#--number=}}); path_done=1 ;;
+      # --number takes one or more values, comma-separated or repeated.
+      --number)
+        path_done=1
+        while (( i < n )) && [[ "$args[i+1]" != -* ]]; do
+          (( i++ ))
+          numbers+=(${(s:,:)args[i]})
+        done
+        ;;
+      # The output flag is global, so it can appear before the subcommand.
+      -o|--output|--format) (( i++ )) ;;
+      -o*|--output=*|--format=*) ;;
+      -*) path_done=1 ;;
+      *) (( path_done )) || path+=("$arg") ;;
+    esac
+    (( i++ ))
+  done
+
+  case "${(j: :)path[1,3]}" in
+    "logs metrics delete")
+      REPLY="deleting a log-derived metric cannot be undone."
+      return 0
+      ;;
+    "logs triggers delete")
+      REPLY="deleting a log-based trigger cannot be undone."
+      return 0
+      ;;
+    "triggers archive")
+      REPLY="archiving a trigger also closes its alerts and incidents."
+      return 0
+      ;;
+    "incidents update")
+      if [[ "${(U)state}" == CLOSED ]] && (( $#numbers > 1 )); then
+        REPLY="this closes $#numbers incidents at once."
+        return 0
+      fi
+      ;;
+  esac
+
+  return 1
+}
+
+# Adds a confirmation prompt before irreversible operations. Everything else
+# passes straight through, so `logs tail` keeps streaming and pipes stay clean.
+function appsignal-cli() {
+  local REPLY
+  if _appsignal_cli_is_destructive "$@"; then
+    print -u2 -- "appsignal-cli: $REPLY"
+    if ! read -q "?Continue? [y/N] "; then
+      print -u2 -- ""
+      return 130
+    fi
+    print -u2 -- ""
+  fi
+
+  command appsignal-cli "$@"
+}
+
+# Complete the aliases like the commands they stand in for.
+if (( $+functions[compdef] )); then
+  _aslog() {
+    words=(appsignal-cli logs tail ${words[2,-1]})
+    (( CURRENT += 2 ))
+    _appsignal-cli
+  }
+
+  _asinc() {
+    words=(appsignal-cli incidents list ${words[2,-1]})
+    (( CURRENT += 2 ))
+    _appsignal-cli
+  }
+
+  compdef _appsignal-cli asig
+  compdef _aslog aslog
+  compdef _asinc asinc
+fi
+
+alias asig='appsignal-cli'
+alias aslog='appsignal-cli logs tail'
+alias asinc='appsignal-cli incidents list'