[RFC] move gitignore file to .devbox directory and ignore gen/profile/shell_history (#215)

## Summary

With the recent use of nix-profile, the `profile` symlinks are showing
up in git history.
This is regrettable.

This PR adds a `.gitignore` file to `.devbox` directory and ignoring the
`gen/`, `profile*`
, `nix-profile` and `shell-history` symlinks.

Going forward, we should avoid editing this file. Each edit will need to
be checked
in by our users. So, this PR is a breaking change, in a sense.

New features we add that generate files in `.devbox` should be added
inside `gen/`
if they want to be gitignored.

New features that we do want users to check in (like a lock file) can be
placed
in `.devbox/` (and not `.devbox/gen`).

## How was it tested?

in a new devbox project, with `git init` and initial files already
committed:
- did `devbox shell` to generate the gitignore and other files 
- did `git status` to inspect changes and found no new file changes were
reported.
- did `ls -al .devbox` and saw the other files (like gen/ and profile*
were generated) as well as `.devbox/.gitignore`.

Author: savil

generate.go

@@ -20,8 +20,8 @@ import (
 //go:embed tmpl/* tmpl/.*
 var tmplFS embed.FS
 
-var shellFiles = []string{".gitignore", "development.nix", "shell.nix"}
-var buildFiles = []string{".gitignore", "development.nix", "runtime.nix", "Dockerfile", "Dockerfile.dockerignore"}
+var shellFiles = []string{"development.nix", "shell.nix"}
+var buildFiles = []string{"development.nix", "runtime.nix", "Dockerfile", "Dockerfile.dockerignore"}
 
 func generate(rootPath string, plan *plansdk.Plan, files []string) error {
 	outPath := filepath.Join(rootPath, ".devbox/gen")
@@ -33,6 +33,14 @@ func generate(rootPath string, plan *plansdk.Plan, files []string) error {
 		}
 	}
 
+	// Gitignore file is added to the .devbox directory
+	// TODO savil. Remove this hardcode from here, so this function can be generically defined again
+	//    by accepting the files list parameter.
+	err := writeFromTemplate(filepath.Join(rootPath, ".devbox"), plan, ".gitignore")
+	if err != nil {
+		return errors.WithStack(err)
+	}
+
 	for name, content := range plan.GeneratedFiles {
 		filePath := filepath.Join(outPath, name)
 		if err := os.WriteFile(filePath, []byte(content), 0644); err != nil {

tmpl/.gitignore.tmpl

@@ -1,2 +1,2 @@
 *
-.*
+.*