Update MD051/link-fragments to identify and fix scenarios where the link fragment has the wrong case (fixes #605).

test/snapshots/markdownlint-test-scenarios.js.md

@@ -21814,12 +21814,16 @@ Generated by [AVA](https://avajs.dev).
         },
         {
           errorContext: '[Invalid](#hrefandid)',
-          errorDetail: null,
+          errorDetail: 'Expected: #HREFandID; Actual: #hrefandid',
           errorRange: [
             1,
             21,
           ],
-          fixInfo: null,
+          fixInfo: {
+            deleteCount: 10,
+            editColumn: 11,
+            insertText: '#HREFandID',
+          },
           lineNumber: 152,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
@@ -21889,6 +21893,59 @@ Generated by [AVA](https://avajs.dev).
             'link-fragments',
           ],
         },
+        {
+          errorContext: '[Title](#Valid-Fragments)',
+          errorDetail: 'Expected: #valid-fragments; Actual: #Valid-Fragments',
+          errorRange: [
+            1,
+            25,
+          ],
+          fixInfo: {
+            deleteCount: 16,
+            editColumn: 9,
+            insertText: '#valid-fragments',
+          },
+          lineNumber: 166,
+          ruleDescription: 'Link fragments should be valid',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
+          ruleNames: [
+            'MD051',
+            'link-fragments',
+          ],
+        },
+        {
+          errorContext: '[ALL CAPS](#NAMEDLINK)',
+          errorDetail: 'Expected: #namedlink; Actual: #NAMEDLINK',
+          errorRange: [
+            1,
+            22,
+          ],
+          fixInfo: {
+            deleteCount: 10,
+            editColumn: 12,
+            insertText: '#namedlink',
+          },
+          lineNumber: 168,
+          ruleDescription: 'Link fragments should be valid',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
+          ruleNames: [
+            'MD051',
+            'link-fragments',
+          ],
+        },
+        {
+          errorContext: '#idLINK',
+          errorDetail: 'Expected: #idlink; Actual: #idLINK',
+          errorRange: null,
+          fixInfo: null,
+          lineNumber: 170,
+          ruleDescription: 'Link fragments should be valid',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
+          ruleNames: [
+            'MD051',
+            'link-fragments',
+          ],
+        },
       ],
       fixed: `# Valid/Invalid Link Fragments␊
       ␊
@@ -22041,7 +22098,7 @@ Generated by [AVA](https://avajs.dev).
       ␊
       [Invalid](#myname) {MD051}␊
       ␊
-      [Invalid](#hrefandid) {MD051}␊
+      [Invalid](#HREFandID) {MD051}␊
       ␊
       [Invalid](#name-for-other-element) {MD051}␊
       ␊
@@ -22053,6 +22110,16 @@ Generated by [AVA](https://avajs.dev).
       ␊
       [badref]: #missing␊
       ␊
+      ## Inconsistent Case Fragments␊
+      ␊
+      [Title](#valid-fragments) {MD051}␊
+      ␊
+      [ALL CAPS](#namedlink) {MD051}␊
+      ␊
+      [MiXeD][mixedref] {MD051}␊
+      ␊
+      [mixedref]: #idLINK␊
+      ␊
       <!-- markdownlint-configure-file {␊
         "emphasis-style": false,␊
         "heading-style": false,␊