Change GitDefaultBranch to main instead of master

It's been a while and most repos I encounter nowadays have switched.

Update docs, change to new default.

Closes #167

readme.md

@@ -212,7 +212,7 @@ Available [MSBuild properties](https://learn.microsoft.com/en-us/visualstudio/ms
 
   $(GitDefaultBranch): determines the base branch used to 
                        calculate commits on top of current branch.
-                       Defaults to 'master'.
+                       Defaults to 'main'.
 
   $(GitVersionFile): determines the name of a file in the Git 
                      repository root used to provide the base 

src/GitInfo/build/GitInfo.targets

@@ -28,7 +28,7 @@
 
 	$(GitDefaultBranch): determines the base branch used to
 						 calculate commits on top of current branch.
-						 Defaults to 'master'.
+						 Defaults to 'main'.
 
 	$(GitVersionFile): determines the name of a file in the Git
 					   repository root used to provide the base
@@ -98,7 +98,7 @@
     <!-- Look it upwards and grab the first one we find. -->
     <GitVersionFile Condition="'$([MSBuild]::GetDirectoryNameOfFileAbove($(GitInfoBaseDir), $(GitVersionFile)))' != ''">$([MSBuild]::GetDirectoryNameOfFileAbove($(GitInfoBaseDir), $(GitVersionFile)))\$(GitVersionFile)</GitVersionFile>
 
-    <GitDefaultBranch Condition="'$(GitDefaultBranch)' == ''">master</GitDefaultBranch>
+    <GitDefaultBranch Condition="'$(GitDefaultBranch)' == ''">main</GitDefaultBranch>
     <GitDefaultCommit Condition="'$(GitDefaultCommit)' == ''">0000000</GitDefaultCommit>
     <GitDefaultVersion Condition="'$(GitDefaultVersion)' == ''">0.0.0</GitDefaultVersion>