Resolve 2px creation, but need a better implementation of conditional run

install.py

@@ -54,7 +54,7 @@ class Installer:
 
         ui.info_2("Cloning", url, "->", pretty_dest)
         git_command = "git clone {} {} --branch {}".format(url, p_dest, branch)
-        subprocess.run(git_command, check=True)
+        subprocess.run(git_command, check=True, shell=True)
 
     def do_copy(self, src: str, dest: str) -> None:
         """Copy two files."""
@@ -133,7 +133,7 @@ class Installer:
 
         src_full.symlink(p_dest)
 
-    def do_update(self, command: str) -> None:
+    def do_run_update(self, command: str) -> None:
         """Run a command only if self.update is True."""
 
         if self.update:
@@ -141,9 +141,25 @@ class Installer:
         else:
             ui.info_2("Skipping", "`{}`".format(command))
 
+    def do_run_no_update(self, command: str) -> None:
+        """Run a command only if self.update is False."""
+
+        if not self.update:
+            self.do_run(command)
+        else:
+            ui.info_2("Skipping", "`{}`".format(command))
+
+    def do_append(self, dest: str, content: str) -> None:
+        """Append to a file."""
+
+        self._do_write(dest, content, append=True)
+
     def do_write(self, dest: str, content: str) -> None:
         """Write into a file."""
 
+        self._do_write(dest, content, append=False)
+
+    def _do_write(self, dest: str, content: str, *, append: bool) -> None:
         p_dest = Path(dest).expanduser()
         pretty_dest = self.pretty_path(p_dest)
 
@@ -158,7 +174,7 @@ class Installer:
         if not content.endswith("\n"):
             content += "\n"
 
-        p_dest.write_text(content)
+        p_dest.write_text(content, append=append)
 
     def install(self, programs: Optional[List[str]] = None) -> None:
         """Install the programs provided.