installer: refuse illegal default branch names

When the user wants to override the default branch name, it is all too
easy to make a mistake and slip e.g. a trailing space in. Let's help
users by preventing such mistakes.

Note: technically the correct way would _not_ be to reimplement
`check_ref_format()`, but at the stage when we want to let the user
specify the branch name, we do not necessarily have a working `git.exe`
to call. That's why the logic was reimplemented (without regular
expressions! Yay Pascal!).

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

Author: dscho

installer/install.iss

@@ -1631,6 +1631,28 @@ begin
         WizardForm.ActiveControl:=EdtDefaultBranch;
 end;
 
+procedure DefaultBranchNameChanged(Sender: TObject);
+var
+    IsValidBranchName:Boolean;
+begin
+    if EdtDefaultBranch.Enabled then begin
+        // Disallow illegal ref names
+        with EdtDefaultBranch do
+            IsValidBranchName:=(Text<>'') and (Text<>'@') and
+                    (Pos('..',Text)=0) and (Pos('@{',Text)=0) and (Pos('//',Text)=0) and
+                    (Pos(#8,Text)=0) and (Pos(' ',Text)=0) and (Pos(':',Text)=0) and
+                    (Pos('?',Text)=0) and (Pos('[',Text)=0) and (Pos('\',Text)=0) and
+                    (Pos('^',Text)=0) and (Pos('~',Text)=0) and (Pos(#127,Text)=0) and
+                    (Pos('/.','/'+Text)=0) and (Pos('./',Text+'/')=0) and (Pos('.lock/',Text+'/')=0);
+        if (WizardForm.CurPageID=DefaultBranchPage.ID) then
+            Wizardform.NextButton.Enabled:=IsValidBranchName;
+        if IsValidBranchName then
+            EdtDefaultBranch.Color:=clWhite
+        else
+            EdtDefaultBranch.Color:=clRed;
+    end;
+end;
+
 procedure QueryUninstallValues; forward;
 
 procedure InitializeWizard;
@@ -1888,6 +1910,7 @@ begin
     TabOrder:=TabOrder+1;
     EdtDefaultBranch.Text:='main';
     EdtDefaultBranch.Enabled:=False;
+    EdtDefaultBranch.OnChange:=@DefaultBranchNameChanged;
     Top:=Top+13+24;
 
     LblInfo:=TLabel.Create(DefaultBranchPage);
@@ -1905,6 +1928,7 @@ begin
         RdbDefaultBranch[DB_Manual].Checked:=True;
         EdtDefaultBranch.Text:=Data;
         EdtDefaultBranch.Enabled:=True;
+        DefaultBranchNameChanged(NIL);
     end end;
 
     (*