docs(Plugin Developer Guide): More detailed lifecycle list and context descriptions (#1880)

* docs(Plugin Developer Guide): More detailed lifecycle list and context descriptions

This commit will improve the following in the Plugin developer guide:
  * Lifecyle list more complete (previous was missing some lifecycles)
  * Context object has been now described in more detail per lifecycle
  * Some readability/maintainability fixes to the markdown file itself
    to make it easier to edit and read in an editor.

* docs(Plugin Developer Guide): Added missing context field to analyzeCommits lifecycle documentation

analyzeCommits lifecycle context was missing documentation for "commits" list.

* docs(developer-guide): remove line breaks added in an earlier commit

As per requested in the code review, the line breaks that were added in an earlier commit are now
removed. While this does make reading the text just slightly more difficult (to see the whole
picture), the benefit of making code reviews easier does outweight the admittedly small benefit.

docs/developer-guide/plugin.md

@@ -1,15 +1,18 @@
 # Plugin Developer Guide
 
-To create a plugin for `semantic-release`, you need to decide which parts of the release lifecycle are important to that plugin. For example, it is best to always have a `verify` step because you may be receiving inputs from a user and want to make sure they exist. A plugin can abide by any of the following lifecycles:
+To create a plugin for `semantic-release`, you need to decide which parts of the release lifecycle are important to that plugin. For example, it is best to always have a `verifyConditions` step because you may be receiving inputs from a user and want to make sure they exist. A plugin can abide by any of the following lifecycles:
 
-- `analyzeCommits`
 - `verifyConditions`
+- `analyzeCommits`
+- `verifyRelease`
+- `generateNotes`
+- `addChannel`
 - `prepare`
 - `publish`
 - `success`
 - `fail`
 
-`semantic-release` will require the plugin via `node` and look through the required object for methods named like the lifecyles stated above. For example, if your plugin only had a `verify` and `success` step, the `main` file for your object would need to `export` an object with `verify` and `success` functions.
+`semantic-release` will require the plugin via `node` and look through the required object for methods named like the lifecyles stated above. For example, if your plugin only had a `verifyConditions` and `success` step, the `main` file for your object would need to `export` an object with `verifyConditions` and `success` functions.
 
 In addition to the lifecycle methods, each lifecyle is passed two objects:
 
@@ -94,7 +97,131 @@ if (message.length) {
 }
 ```
 
-## Supporting Environment Variables
+## Context
+
+### Common context keys
+
+* `stdout`
+* `stderr`
+* `logger`
+
+### Context object keys by lifecycle
+
+#### verifyConditions
+
+Initially the context object contains the following keys (`verifyConditions` lifecycle):
+* `cwd`
+  * Current working directory
+* `env`
+  * Environment variables
+* `envCi`
+  * Information about CI environment
+  * Contains (at least) the following keys:
+    * `isCi`
+      * Boolean, true if the environment is a CI environment
+    * `commit`
+      * Commit hash
+    * `branch`
+      * Current branch
+* `options`
+  * Options passed to `semantic-release` via CLI, configuration files etc.
+* `branch`
+  * Information on the current branch
+  * Object keys:
+    * `channel`
+    * `tags`
+    * `type`
+    * `name`
+    * `range`
+    * `accept`
+    * `main`
+* `branches`
+  * Information on branches
+  * List of branch objects (see above)
+
+#### analyzeCommits
+
+Compared to the verifyConditions, `analyzeCommits` lifecycle context has keys
+
+* `commits` (List)
+  * List of commits taken into account when determining the new version.
+  * Keys:
+    * `commit` (Object)
+      * Keys:
+        * `long` (String, Commit hash)
+        * `short` (String, Commit hash)
+    * `tree` (Object)
+      * Keys:
+        * `long` (String, Commit hash)
+        * `short` (String, Commit hash)
+    * `author` (Object)
+      * Keys:
+        * `name` (String)
+        * `email` (String)
+        * `date` (String, ISO 8601 timestamp)
+    * `committer` (Object)
+      * Keys:
+        * `name` (String)
+        * `email` (String)
+        * `date` (String, ISO 8601 timestamp)
+    * `subject` (String, Commit message subject)
+    * `body` (String, Commit message body)
+    * `hash` (String, Commit hash)
+    * `committerDate` (String, ISO 8601 timestamp)
+    * `message` (String)
+    * `gitTags` (String, List of git tags)
+* `releases` (List)
+* `lastRelease` (Object)
+  * Keys
+    * `version` (String)
+    * `gitTag` (String)
+    * `channels` (List)
+    * `gitHead` (String, Commit hash)
+    * `name` (String)
+
+#### verifyRelease
+
+Additional keys:
+
+* `nextRelease`
+  * Similar object as `lastRelease` (see above)
+
+#### generateNotes
+
+No new content in the context.
+
+#### addChannel
+
+*This is run only if there are releases that have been merged from a higher branch but not added on the channel of the current branch.*
+
+Context content is similar to lifecycle `verifyRelease`.
+
+#### prepare
+
+Only change is that `generateNotes` has populated `nextRelease.notes`.
+
+#### publish
+
+No new content in the context.
+
+#### success
+
+Lifecycles `success` and `fail` are mutually exclusive, only one of them will be run.
+
+Additional keys:
+
+* `releases`
+  * Populated by `publish` lifecycle
+
+#### fail
+
+Lifecycles `success` and `fail` are mutually exclusive, only one of them will be run.
+
+Additional keys:
+
+* `errors`
+
+### Supporting Environment Variables
 
 Similar to `options`, environment variables exist to allow users to pass tokens and set special URLs. These are set on the `context` object instead of the `pluginConfig` object. Let's say we wanted to check for `GITHUB_TOKEN` in the environment because we want to post to GitHub on the user's behalf. To do this, we can add the following to our `verify` command:
 
@@ -102,6 +229,6 @@ Similar to `options`, environment variables exist to allow users to pass tokens
 const { env } = context;
 
 if (env.GITHUB_TOKEN) {
-    //...
+  //...
 }
 ```