Handle unknown Git versions appropriately

In the event that some Git version was recorded that isn’t known to the
Git release database, this patch introduces an “unknown” dataset that is
invisible otherwise.

docs/assets/js/_partials/chart-recommended-git-versions.js

@@ -9,7 +9,9 @@ class RecommendedGitVersionsChart extends AreaChart
                 vulnerable: 'red',
                 outdated: 'yellow',
                 recommended: 'green',
+                unknown: 'grey',
             },
+            datasets: ['recommended', 'outdated', 'vulnerable'],
             views:
             [
                 {
@@ -91,6 +93,7 @@ class RecommendedGitVersionsChart extends AreaChart
                     recommended: 0,
                     outdated: 0,
                     vulnerable: 0,
+                    unknown: 0,
                 };
 
             while (version.split('.').length < 3)
@@ -104,6 +107,16 @@ class RecommendedGitVersionsChart extends AreaChart
                 continue;
             }
 
+            if (!(version in gitReleases))
+            {
+                // If an unknown version was found, show the “unknown” dataset
+                if (this.config.datasets.indexOf('unknown') === -1)
+                    this.config.datasets.push('unknown');
+
+                result[date].unknown += users;
+                continue;
+            }
+
             if ('vulnerableSince' in gitReleases[version]
                 && gitReleases[version].vulnerableSince < date)
             {

docs/spec/chart-recommended-git-versions.js

@@ -31,16 +31,19 @@ describe('Recommended Git versions chart', function()
                     expect(chartData[287].vulnerable).toEqual(200);
                     expect(chartData[287].outdated).toEqual(188);
                     expect(chartData[287].recommended).toEqual(60);
+                    expect(chartData[287].unknown).toEqual(0);
 
                     expect(chartData[84].date).toEqual(new Date('2018-10-08'));
                     expect(chartData[84].vulnerable).toEqual(657);
                     expect(chartData[84].outdated).toEqual(0);
                     expect(chartData[84].recommended).toEqual(51);
+                    expect(chartData[84].unknown).toEqual(0);
 
                     expect(chartData[21].date).toEqual(new Date('2018-12-10'));
                     expect(chartData[21].vulnerable).toEqual(713);
                     expect(chartData[21].outdated).toEqual(146);
                     expect(chartData[21].recommended).toEqual(178);
+                    expect(chartData[21].unknown).toEqual(0);
 
                     done();
                 });