Add 'changed-files-labels-limit' and 'max-files-changed' configs to allow capping number of labels added (#923)

* README.md: drop trailing whitespace

* Add 'changed-files-labels-limit' config to allow capping number of labels added

When a repository has many components, each with a changed-files label,
a large refactor ends up with the labeler spamming the pull request
with label changes. The end result is not very useful as it's not
very readable, and due to how github automatically hides comments
when label changes overflow the discussion tab, it means useful
information is hidden and one has to manually click "Load more..."
dozens of time every time the page is loaded.

Add a changed-files-labels-limit top level config knob. If more than the
configured limit of labels is set to be added, none are added.
This only affects changed-files labels.

* Add 'max-files-changed' config to allow capping number of files for labelling

When a PR modifies a very large number of files (e.g., tree-wide
refactors, automated code formatting), this new options allows
skipping file-based labeling entirely when the number of files
that are changed hits the configured limit.

Fixes https://github.com/actions/labeler/issues/486

__tests__/fixtures/limit_0.yml

@@ -0,0 +1,18 @@
+# Limit to 0 changed-files labels (none allowed)
+changed-files-labels-limit: 0
+
+# Labels based on changed files
+component-a:
+  - changed-files:
+      - any-glob-to-any-file: ['components/a/**']
+
+component-b:
+  - changed-files:
+      - any-glob-to-any-file: ['components/b/**']
+
+# Labels based on branch patterns only
+test-branch:
+  - head-branch: '^test/'
+
+feature-branch:
+  - head-branch: '/feature/'

__tests__/fixtures/limit_1.yml

@@ -0,0 +1,26 @@
+# Limit to 1 changed-files label
+changed-files-labels-limit: 1
+
+# Labels based on changed files
+component-a:
+  - changed-files:
+      - any-glob-to-any-file: ['components/a/**']
+
+component-b:
+  - changed-files:
+      - any-glob-to-any-file: ['components/b/**']
+
+component-c:
+  - changed-files:
+      - any-glob-to-any-file: ['components/c/**']
+
+component-d:
+  - changed-files:
+      - any-glob-to-any-file: ['components/d/**']
+
+# Labels based on branch patterns only
+test-branch:
+  - head-branch: '^test/'
+
+feature-branch:
+  - head-branch: '/feature/'

__tests__/fixtures/limit_2.yml

@@ -0,0 +1,26 @@
+# Limit to 2 changed-files labels
+changed-files-labels-limit: 2
+
+# Labels based on changed files
+component-a:
+  - changed-files:
+      - any-glob-to-any-file: ['components/a/**']
+
+component-b:
+  - changed-files:
+      - any-glob-to-any-file: ['components/b/**']
+
+component-c:
+  - changed-files:
+      - any-glob-to-any-file: ['components/c/**']
+
+component-d:
+  - changed-files:
+      - any-glob-to-any-file: ['components/d/**']
+
+# Labels based on branch patterns only
+test-branch:
+  - head-branch: '^test/'
+
+feature-branch:
+  - head-branch: '/feature/'

__tests__/fixtures/limit_3.yml

@@ -0,0 +1,26 @@
+# Limit to 3 changed-files labels
+changed-files-labels-limit: 3
+
+# Labels based on changed files
+component-a:
+  - changed-files:
+      - any-glob-to-any-file: ['components/a/**']
+
+component-b:
+  - changed-files:
+      - any-glob-to-any-file: ['components/b/**']
+
+component-c:
+  - changed-files:
+      - any-glob-to-any-file: ['components/c/**']
+
+component-d:
+  - changed-files:
+      - any-glob-to-any-file: ['components/d/**']
+
+# Labels based on branch patterns only
+test-branch:
+  - head-branch: '^test/'
+
+feature-branch:
+  - head-branch: '/feature/'

__tests__/fixtures/max_files_5.yml

@@ -0,0 +1,15 @@
+# Skip file-based labeling if more than 5 files changed
+max-files-changed: 5
+
+# Labels based on changed files
+component-a:
+  - changed-files:
+      - any-glob-to-any-file: ['components/a/**']
+
+component-b:
+  - changed-files:
+      - any-glob-to-any-file: ['components/b/**']
+
+component-c:
+  - changed-files:
+      - any-glob-to-any-file: ['components/c/**']

__tests__/fixtures/max_files_with_branch.yml

@@ -0,0 +1,15 @@
+# Skip file-based labeling if more than 3 files changed
+max-files-changed: 3
+
+# Labels based on changed files
+component-a:
+  - changed-files:
+      - any-glob-to-any-file: ['components/a/**']
+
+component-b:
+  - changed-files:
+      - any-glob-to-any-file: ['components/b/**']
+
+# Branch-based label (should not be affected)
+test-branch:
+  - head-branch: ['^test/']

__tests__/fixtures/mixed_labels.yml

@@ -0,0 +1,23 @@
+# Labels based on changed files
+component-a:
+  - changed-files:
+      - any-glob-to-any-file: ['components/a/**']
+
+component-b:
+  - changed-files:
+      - any-glob-to-any-file: ['components/b/**']
+
+component-c:
+  - changed-files:
+      - any-glob-to-any-file: ['components/c/**']
+
+component-d:
+  - changed-files:
+      - any-glob-to-any-file: ['components/d/**']
+
+# Labels based on branch patterns only
+test-branch:
+  - head-branch: '^test/'
+
+feature-branch:
+  - head-branch: '/feature/'

__tests__/fixtures/mixed_rules.yml

@@ -0,0 +1,16 @@
+# Test fixture for mixed rules behavior
+# A label with both branch and changed-files rules is considered a "changed-files label"
+# and is subject to the limit, even if it matches via the branch rule
+changed-files-labels-limit: 0
+
+# This label has both branch and changed-files rules
+# It should be subject to the limit even if matched via branch
+mixed-label:
+  - any:
+      - head-branch: '^test/'
+      - changed-files:
+          - any-glob-to-any-file: ['components/a/**']
+
+# Pure branch-based label - not subject to limit
+pure-branch-label:
+  - head-branch: '^test/'