installer: default to GCM Core (including fresh installs)

We just worked on the installer to auto-upgrade existing GCM(W) users to
GCM Core.

What we did _not_ do is to default new users to GCM Core. D'oh.

Noticed by Matthew Cheetham.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

installer/install.iss

@@ -2128,10 +2128,10 @@ begin
             'Enabled': RdbGitCredentialManager[GCM_Classic].Checked:=True;
             'Core': RdbGitCredentialManager[GCM_Core].Checked:=True;
         else
-            RdbGitCredentialManager[GCM_Classic].Checked:=True;
+            RdbGitCredentialManager[GCM_Core].Checked:=True;
         end;
         // Auto-upgrade GCM to GCM Core in version v2.29.0
-        if RdbGitCredentialManager[GCM_Classic].Checked and (PreviousGitForWindowsVersion<>'') and IsDowngrade(PreviousGitForWindowsVersion,'2.29.0') then begin
+        if RdbGitCredentialManager[GCM_Classic].Checked and ((PreviousGitForWindowsVersion='') or IsDowngrade(PreviousGitForWindowsVersion,'2.29.0')) then begin
             RdbGitCredentialManager[GCM_Core].Checked:=True;
             AddToSet(CustomPagesWithUnseenOptions,GitCredentialManagerPage);
         end;