Add convenience builder for git commands

Adds a convenience builder for git commands. Applies it in a couple of places that benefit from it.

I've got a larger PR that does a more sweeping change but I want some reviews on that before I go ahead with it.

pkg/commands/git_commands/git_command_builder.go

@@ -0,0 +1,65 @@
+package git_commands
+
+import "fmt"
+
+// convenience struct for building git commands. Especially useful when
+// including conditional args
+type GitCommandBuilder struct {
+	command string
+}
+
+func NewGitCmd(command string) *GitCommandBuilder {
+	return &GitCommandBuilder{command: command}
+}
+
+func (self *GitCommandBuilder) Arg(flag string) *GitCommandBuilder {
+	if flag == "" {
+		return self
+	}
+
+	self.command += " " + flag
+
+	return self
+}
+
+func (self *GitCommandBuilder) ArgIf(include bool, flag string) *GitCommandBuilder {
+	if include {
+		return self.Arg(flag)
+	}
+
+	return self
+}
+
+func (self *GitCommandBuilder) ArgIfElse(isTrue bool, onTrue string, onFalse string) *GitCommandBuilder {
+	if isTrue {
+		return self.Arg(onTrue)
+	} else {
+		return self.Arg(onFalse)
+	}
+}
+
+func (self *GitCommandBuilder) Args(args []string) *GitCommandBuilder {
+	for _, arg := range args {
+		self.Arg(arg)
+	}
+
+	return self
+}
+
+func (self *GitCommandBuilder) Config(value string) *GitCommandBuilder {
+	// config settings come before the command
+	self.command = fmt.Sprintf("-c %s %s", value, self.command)
+
+	return self
+}
+
+func (self *GitCommandBuilder) RepoPath(value string) *GitCommandBuilder {
+	// repo path comes before the command
+	self.command = fmt.Sprintf("-C %s %s", value, self.command)
+
+	return self
+}
+
+func (self *GitCommandBuilder) ToString() string {
+	return "git " + self.command
+}