Make coder dotfiles symlinking idempotent (#7525)

Signed-off-by: Spike Curtis <spike@coder.com>

cli/dotfiles.go

@@ -225,6 +225,10 @@ func (r *RootCmd) dotfiles() *clibase.Cmd {
 					}
 				}
 
+				// attempt to delete the file before creating a new symlink.  This overwrites any existing symlinks
+				// which are typically leftover from a previous call to coder dotfiles.  We do this best effort and
+				// ignore errors because the symlink may or may not exist.  Any regular files are backed up above.
+				_ = os.Remove(to)
 				err = os.Symlink(from, to)
 				if err != nil {
 					return xerrors.Errorf("symlinking %s to %s: %w", from, to, err)

cli/dotfiles_test.go

@@ -116,6 +116,17 @@ func TestDotfiles(t *testing.T) {
 		b, err = os.ReadFile(filepath.Join(string(root), ".bashrc.bak"))
 		require.NoError(t, err)
 		require.Equal(t, string(b), "backup")
+
+		// check for idempotency
+		inv, _ = clitest.New(t, "dotfiles", "--global-config", string(root), "--symlink-dir", string(root), "-y", testRepo)
+		err = inv.Run()
+		require.NoError(t, err)
+		b, err = os.ReadFile(filepath.Join(string(root), ".bashrc"))
+		require.NoError(t, err)
+		require.Equal(t, string(b), "wow")
+		b, err = os.ReadFile(filepath.Join(string(root), ".bashrc.bak"))
+		require.NoError(t, err)
+		require.Equal(t, string(b), "backup")
 	})
 }