feat(validation): add option to exclude a list of commits by sha

This adds a new configuration option, `excluded-commits`, which allows
the user to provide a list of commits (full SHA1; 40 characters) that
will be skipped during validation runs.

This is useful for instance when having to merge branches from other,
less strictly checked repo's.

docs/configuration.md

@@ -30,6 +30,7 @@ initial-development: false  # OPTIONAL, defaults to `true`
 | `allowed-branches` | `.*` | A regex specifying from which branch(es) releases and Git tags are allowed to be created |
 | `initial-development` | `true` | A boolean indicating that this project is still under _initial development_. During this state, any commit message containing a breaking change will result in a `MINOR` version bump. |
 | `sdkver-create-release-branches` | `false` | For SdkVer versioning scheme only: push a new branch if an RC or release build is performed on a non-release branch. If this config value is boolean `true`, the branch shall be of the form `release/N.N`. If this value is set to a string, it shall be used as the branch name prefix and appended with the major and minor release numbers, e.g. config value  `"rel/"` results in a branch named `rel/N.N`. |
+| `excluded-commits` | `[]` | An optional list of (40-character) SHA1 hashes representing commits (and their ancestry) that should not be checked. For example, when merging another repo/branch with non-conventional-commits, add the SHA of that repo/branch's HEAD to the list, which allows it to pass the validation action. |
 
 > :bulb: By default `commisery-action` will search for the file `.commisery.yml`. 
 You can specify a different file with the `config` input parameter.

src/config.ts

@@ -73,6 +73,7 @@ const CONFIG_ITEMS = [
   "release-branches",
   "prereleases",
   "sdkver-create-release-branches",
+  "excluded-commits",
 ];
 
 const VERSION_SCHEMES = ["semver", "sdkver"];
@@ -107,6 +108,7 @@ export class Configuration {
   tags: IConfigurationRules = DEFAULT_ACCEPTED_TAGS;
   rules: Map<string, IRuleConfigItem> = new Map<string, IRuleConfigItem>();
   sdkverCreateReleaseBranches?: string = undefined;
+  excludedCommits: string[] = [];
 
   set initialDevelopment(initialDevelopment: boolean) {
     this._initialDevelopment = initialDevelopment;
@@ -339,6 +341,25 @@ export class Configuration {
             );
           }
           break;
+
+        case "excluded-commits":
+          /* Example YAML:
+           *   excluded-commits: []
+           *   excluded-commits: ["3723ac94f5091257195d91a26e03492a8265b90d"]
+           *   excluded-commits:
+           *     - 3723ac94f5091257195d91a26e03492a8265b90d
+           *     - 1234567890123456789012345678901234567890
+           */
+          if (typeof data[key] === "object") {
+            this.excludedCommits = data[key] as string[];
+          } else {
+            throw new Error(
+              `Incorrect type '${typeof data[
+                key
+              ]}' for '${key}', must be an array of strings!`
+            );
+          }
+          break;
       }
     }
     if (