fix: Strip preffixes correclty

Author: DReigada

spec/git-version-spec.cr

@@ -319,7 +319,7 @@ describe GitVersion do
       tmp.exec %(git merge myfeature)
 
       tmp.exec %(git checkout master)
-      tmp.exec %(git rebase dev)
+      tmp.exec %(git rebase --no-gpg-sign dev)
       version = git.get_version
       version.should eq("1.0.1")
     ensure
@@ -345,7 +345,7 @@ describe GitVersion do
 
       tmp.exec %(git checkout dev)
       tmp.exec %(git commit --no-gpg-sign --allow-empty -m "4")
-      tmp.exec %(git rebase master)
+      tmp.exec %(git rebase --no-gpg-sign master)
 
       tmp.exec %(git checkout master)
       tmp.exec %(git merge --no-gpg-sign --no-ff dev)

src/git-version.cr

@@ -24,12 +24,7 @@ module GitVersion
     end
 
     private def strip_prefix(version : String) : String | Nil
-      stripped = version.lstrip(@prefix)
-      if @prefix != "" && stripped.size >= version.size
-        nil
-      else
-        stripped
-      end
+      version.lchop?(@prefix)
     end
 
     private def exec(cmd)