Handle pending actions properly in git commands that require credentials

I don't know if this is a hack or not: we run a git command and increment the pending action
count to 1 but at some point the command requests a username or password, so we need to prompt
the user to enter that. At that point we don't want to say that there is a pending action,
so we decrement the action count before prompting the user and then re-increment it again afterward.

Given that we panic when the counter goes below zero, it's important that it's not zero
when we run the git command (should be impossible anyway).

I toyed with a different approach using channels and a long-running goroutine that
handles all commands that request credentials but it feels over-engineered compared to this
commit's approach.

pkg/commands/oscommands/gui_io.go

@@ -26,15 +26,27 @@ type guiIO struct {
 	// this allows us to request info from the user like username/password, in the event
 	// that a command requests it.
 	// the 'credential' arg is something like 'username' or 'password'
-	promptForCredentialFn func(credential CredentialType) string
+	promptForCredentialFn func(credential CredentialType) <-chan string
+
+	IncrementBusyCount func()
+	DecrementBusyCount func()
 }
 
-func NewGuiIO(log *logrus.Entry, logCommandFn func(string, bool), newCmdWriterFn func() io.Writer, promptForCredentialFn func(CredentialType) string) *guiIO {
+func NewGuiIO(
+	log *logrus.Entry,
+	logCommandFn func(string, bool),
+	newCmdWriterFn func() io.Writer,
+	promptForCredentialFn func(CredentialType) <-chan string,
+	IncrementBusyCount func(),
+	DecrementBusyCount func(),
+) *guiIO {
 	return &guiIO{
 		log:                   log,
 		logCommandFn:          logCommandFn,
 		newCmdWriterFn:        newCmdWriterFn,
 		promptForCredentialFn: promptForCredentialFn,
+		IncrementBusyCount:    IncrementBusyCount,
+		DecrementBusyCount:    DecrementBusyCount,
 	}
 }
 
@@ -46,5 +58,7 @@ func NewNullGuiIO(log *logrus.Entry) *guiIO {
 		logCommandFn:          func(string, bool) {},
 		newCmdWriterFn:        func() io.Writer { return io.Discard },
 		promptForCredentialFn: failPromptFn,
+		IncrementBusyCount:    func() {},
+		DecrementBusyCount:    func() {},
 	}
 }