Add support for exclusions (actions#22)

* Add support for exclusions

Paths can be negated to stop searching through the remaining patterns in
a the glob list. All changed files tested and at least one matching file
will result in a label being added.

Fixes actions#9

* Add support for "AND"-ed matches

A new "rich" matcher object can be provided instead of a normal glob.

The matcher object has two fields that accept an array of globs:
* Globs in "all" must all match every changed file.
* Globs in "some" must all match at least one changed file.

Combined with negated globs, this allows for a precise control of when
labels are applied.

* Rename `some` to `any`

* Update README

README.md

@@ -10,7 +10,35 @@ Note that only pull requests being opened from the same repository can be labele
 
 Create a `.github/labeler.yml` file with a list of labels and [minimatch](https://github.com/isaacs/minimatch) globs to match to apply the label.
 
-The key is the name of the label in your repository that you want to add (eg: "merge conflict", "needs-updating") and the value is the path (glob) of the changed files (eg: `src/**/*`, `tests/*.spec.js`)
+The key is the name of the label in your repository that you want to add (eg: "merge conflict", "needs-updating") and the value is the path (glob) of the changed files (eg: `src/**/*`, `tests/*.spec.js`) or a match object.
+
+#### Match Object
+
+For more control over matching, you can provide a match object instead of a simple path glob. The match object is defined as:
+
+```yml
+- any: ['list', 'of', 'globs']
+  all: ['list', 'of', 'globs']
+```
+
+One or both fields can be provided for fine-grained matching. Unlike the top-level list, the list of path globs provided to `any` and `all` must ALL match against a path for the label to be applied.
+
+The fields are defined as follows:
+* `any`: match ALL globs against ANY changed path
+* `all`: match ALL globs against ALL changed paths
+
+A simple path glob is the equivalent to `any: ['glob']`. More specifically, the following two configurations are equivalent:
+```yml
+label1:
+- example1/*
+```
+and
+```yml
+label1:
+- any: ['example1/*']
+```
+
+From a boolean logic perspective, top-level match objects are `OR`-ed together and indvidual match rules within an object are `AND`-ed. Combined with `!` negation, you can write complex matching rules.
 
 #### Basic Examples
 
@@ -38,6 +66,15 @@ repo:
 # Add 'test' label to any change to *.spec.js files within the source dir
 test:
   - src/**/*.spec.js
+
+# Add 'source' label to any change to src files within the source dir EXCEPT for the docs sub-folder
+source:
+- any: ['src/**/*', '!src/docs/*']
+
+# Add 'frontend` label to any change to *.js files as long as the `main.js` hasn't changed
+frontend:
+- any: ['src/**/*.js']
+  all: ['!src/main.js']
 ```
 
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