Fix unified diff hunk header highlight to allow for single-number case

CHANGES.md

@@ -10,13 +10,15 @@ Core Grammars:
 - fix(javascript) correctly highlight 'for await' again [wolfgang42][]
 - enh(csp) add missing directives / keywords from MDN (7 more) [Max Liashuk][]
 - enh(ada) add new `parallel` keyword, allow `[]` for Ada 2022 [Max Reznik][]
+- fix(diff) fix unified diff hunk header regex to allow unpaired numbers [Chris Wilson][]
 - enh(php) support single line and hash comments in attributes, constructor and functions [Antoine Musso][]
 
 CONTRIBUTORS
 
 [Josh Marchand]: https://github.com/yHSJ
 [Max Liashuk]: https://github.com/probil
 [Max Reznik]: https://github.com/reznikmm
+[Chris Wilson]: https://github.com/sushicw
 [Antoine Musso]: https://github.com/hashar
 [Chester Moses]: https://github.com/Chester-Moses-HCL
 

src/languages/diff.js

@@ -17,7 +17,10 @@ export default function(hljs) {
         className: 'meta',
         relevance: 10,
         match: regex.either(
-          /^@@ +-\d+,\d+ +\+\d+,\d+ +@@/,
+          /^@@ +-\d+,\d+ +\+\d+,\d+ +@@/, // @@ -1,2 +1,2 @@
+          /^@@ +-\d+ +\+\d+,\d+ +@@/,     // @@ -1 +1,2 @@
+          /^@@ +-\d+,\d+ +\+\d+ +@@/,     // @@ -1,2 +1 @@
+          /^@@ +-\d+ +\+\d+ +@@/,         // @@ -1 +1 @@
           /^\*\*\* +\d+,\d+ +\*\*\*\*$/,
           /^--- +\d+,\d+ +----$/
         )

test/markup/diff/git-format-patch.expect.txt

@@ -12,3 +12,26 @@
 <span class="hljs-meta">@@ -28,2 +28,2 @@</span>
 <span class="hljs-deletion">- removal</span>
 <span class="hljs-addition">+ addition</span>
+<span class="hljs-comment">diff --git a/file.txt b/file.txt</span>
+<span class="hljs-comment">index 8baef1b..24c5735 100644</span>
+<span class="hljs-comment">--- a/file.txt</span>
+<span class="hljs-comment">+++ b/file.txt</span>
+<span class="hljs-meta">@@ -1 +1 @@</span>
+<span class="hljs-deletion">-removal</span>
+<span class="hljs-addition">+addition</span>
+<span class="hljs-comment">diff --git a/file.txt b/file.txt</span>
+<span class="hljs-comment">index f9308d8..f39c17d 100644</span>
+<span class="hljs-comment">--- a/file.txt</span>
+<span class="hljs-comment">+++ b/file.txt</span>
+<span class="hljs-meta">@@ -1,2 +1 @@</span>
+<span class="hljs-deletion">-removal1</span>
+<span class="hljs-deletion">-removal2</span>
+<span class="hljs-addition">+addition</span>
+<span class="hljs-comment">diff --git a/file.txt b/file.txt</span>
+<span class="hljs-comment">index 1037b05..54addbd 100644</span>
+<span class="hljs-comment">--- a/file.txt</span>
+<span class="hljs-comment">+++ b/file.txt</span>
+<span class="hljs-meta">@@ -1 +1,2 @@</span>
+<span class="hljs-deletion">-removal</span>
+<span class="hljs-addition">+addition1</span>
+<span class="hljs-addition">+addition2</span>

test/markup/diff/git-format-patch.txt

@@ -12,3 +12,26 @@ index 123456..789abc 100644
 @@ -28,2 +28,2 @@
 - removal
 + addition
+diff --git a/file.txt b/file.txt
+index 8baef1b..24c5735 100644
+--- a/file.txt
++++ b/file.txt
+@@ -1 +1 @@
+-removal
++addition
+diff --git a/file.txt b/file.txt
+index f9308d8..f39c17d 100644
+--- a/file.txt
++++ b/file.txt
+@@ -1,2 +1 @@
+-removal1
+-removal2
++addition
+diff --git a/file.txt b/file.txt
+index 1037b05..54addbd 100644
+--- a/file.txt
++++ b/file.txt
+@@ -1 +1,2 @@
+-removal
++addition1
++addition2