Fix exception thrown when buildNumberOffset is -1 and uncommitted

AArnott · AArnott · commit bdfbdceed10d · 2016-12-29T11:54:25.000-08:00
Closes #102
diff --git a/src/NerdBank.GitVersioning/GitExtensions.cs b/src/NerdBank.GitVersioning/GitExtensions.cs
@@ -438,7 +438,7 @@ private static Version GetIdAsVersionHelper(Commit commit, VersionOptions versio
                     : 0;
             }
 
-            int build = versionHeight.Value + (versionOptions?.BuildNumberOffset ?? 0);
+            int build =  versionHeight.Value == 0 ? 0 : versionHeight.Value + (versionOptions?.BuildNumberOffset ?? 0);
             Verify.Operation(build <= MaximumBuildNumberOrRevisionComponent, "Git height is {0}, which is greater than the maximum allowed {0}.", build, MaximumBuildNumberOrRevisionComponent);
             int revision = commit != null
                 ? Math.Min(MaximumBuildNumberOrRevisionComponent, commit.GetTruncatedCommitIdAsUInt16())

Original file line number	Diff line number	Diff line change
`@@ -438,7 +438,7 @@ private static Version GetIdAsVersionHelper(Commit commit, VersionOptions versio`
`438`	`438`	`: 0;`
`439`	`439`	`}`
`440`	`440`
`441`		`- int build = versionHeight.Value + (versionOptions?.BuildNumberOffset ?? 0);`
	`441`	`+ int build = versionHeight.Value == 0 ? 0 : versionHeight.Value + (versionOptions?.BuildNumberOffset ?? 0);`
`442`	`442`	`Verify.Operation(build <= MaximumBuildNumberOrRevisionComponent, "Git height is {0}, which is greater than the maximum allowed {0}.", build, MaximumBuildNumberOrRevisionComponent);`
`443`	`443`	`int revision = commit != null`
`444`	`444`	`? Math.Min(MaximumBuildNumberOrRevisionComponent, commit.GetTruncatedCommitIdAsUInt16())`