feat: Make semantic-release language agnostic

- Do not rely on `package.json` anymore
- Use `cosmiconfig` to load the configation. `semantic-release` can be configured:
  - via CLI options (including plugin names but not plugin options)
  - in the `release` property of `package.json` (as before)
  - in a `.releaserc.yml` or `.releaserc.js` or `.releaserc.js` or `release.config.js` file
  - in a `.releaserc` file containing `json`, `yaml` or `javascript` module
- Add the `repositoryUrl` options (used across `semantic-release` and plugins). The value is determined from CLi option, or option configuration, or package.json or the git remote url
- Verifies that `semantic-release` runs from a git repository
- `pkg` and `env` are not passed to plugin anymore
- `semantic-release` can be run both locally and globally. If ran globally with non default plugins, the plugins can be installed both globally or locally.

BREAKING CHANGE: `pkg` and `env` are not passed to plugin anymore.
Plugins relying on a `package.json` must verify the presence of a valid `package.json` and load it.
Plugins can use `process.env` instead of `env`.

test/helpers/git-utils.js

@@ -1,6 +1,7 @@
 import tempy from 'tempy';
 import execa from 'execa';
-import pMapSeries from 'p-map-series';
+import fileUrl from 'file-url';
+import pReduce from 'p-reduce';
 
 /**
  * Commit message informations.
@@ -33,11 +34,16 @@ export async function gitRepo() {
  * @returns {Array<Commit>} The created commits, in reverse order (to match `git log` order).
  */
 export async function gitCommits(messages) {
-  return (await pMapSeries(messages, async msg => {
-    const {stdout} = await execa('git', ['commit', '-m', msg, '--allow-empty', '--no-gpg-sign']);
-    const [, branch, hash, message] = /^\[(\w+)\(?.*?\)?(\w+)\] (.+)$/.exec(stdout);
-    return {branch, hash, message};
-  })).reverse();
+  return (await pReduce(
+    messages,
+    async (commits, msg) => {
+      const {stdout} = await execa('git', ['commit', '-m', msg, '--allow-empty', '--no-gpg-sign']);
+      const [, branch, hash, message] = /^\[(\w+)\(?.*?\)?(\w+)\] (.+)$/.exec(stdout);
+      commits.push({branch, hash, message});
+      return commits;
+    },
+    []
+  )).reverse();
 }
 
 /**
@@ -109,7 +115,7 @@ export async function gitShallowClone(origin, branch = 'master', depth = 1) {
   const dir = tempy.directory();
 
   process.chdir(dir);
-  await execa('git', ['clone', '--no-hardlinks', '--no-tags', '-b', branch, '--depth', depth, `file://${origin}`, dir]);
+  await execa('git', ['clone', '--no-hardlinks', '--no-tags', '-b', branch, '--depth', depth, fileUrl(origin), dir]);
   return dir;
 }
 
@@ -137,3 +143,13 @@ export async function gitDetachedHead(origin, head) {
 export async function gitPackRefs() {
   await execa('git', ['pack-refs', '--all']);
 }
+
+/**
+ * Add a new Git configuration.
+ *
+ * @param {string} name Config name.
+ * @param {string} value Config value.
+ */
+export async function gitAddConfig(name, value) {
+  await execa('git', ['config', '--add', name, value]);
+}