add dispatch init command

[chicoxyzzy]

This PR implements dispatch init command to initialize a new project.

Usage

dispatch init <template> [path]

Where <template> is a required option and [path] is optional.

Templates directory

On a first use the command will create an Application Data directory dispatch

• Windows: The application data directory is typically located at %APPDATA% or %LOCALAPPDATA%.
• macOS: The application data directory is typically located at $HOME/Library/Application Support.
• Linux: The application data directory is typically located at $XDG_CONFIG_HOME or $HOME/.config.

The App Data directory is used to save templates oh a user's computer to make them available for use later without Internet.
The directory has follows structure:

dispatch/
  templates/
    foo/
    bar/
  templates.sha

Workflow

1. dispatch init <template> will try to get the SHA of the latest commit from the repository and compare it to local SHA. If values differ, Dispatch CLI will download update for templates first.
2. Dispatch CLI makes request to using GitHub REST API to download tarball of the latest commit and then extracts it into the Dispatch's App Data directory.
3. Finally, it copes template's files from the App Data directory (provided as <template> option) to a current working directory or to the [path] if it was provided.

If the destination directory is not empty, user will be asked if they want to clear the directory

Try it

git checkout init_command
make build
./build/darwin/arm64/dispatch init cat-facts ~/dispatch-template-test

This will create cat-facts template in the dispatch-template-test of your home directory.
Note that build directory can be different for your computer's arch and OS

To clear templates cache

rm -rf ~/Library/Application\ Support/dispatch

if you use MacOS

Notes and open questions

• Current PR uses https://github.com/dispatchrun/dispatch-examples as a templates repo for the demonstration purpose only. We should introduce a new repo for templates.
• Should we introduce versioning for templates to make them compatible with different versions of SDKs? I think we should
• We can improve the templates update by adding information about which templates have been added/removed/modified or/and show last N commit messages and link to the full diff on GitHub between two SHAs
• Current implementation makes it pretty easy to add 3rd-party templates (as described in Scaffolding projects with dispatch init command #59), but
  • it is easy to just use git clone instead (although init's caching and templates updating features could be still useful)
  • we should signal user that it is a 3rd-party template and it's not maintained by dispatch.run
• Should dispatch init go to the Dispatch Commands group or should it be in the Additional Commands in the dispatch -h output? it's in the Dispatch group

---

Closes #59

[chicoxyzzy]

This also still needs tests and docs update, but I wanted to start discussion earlier.

[achille-roussel]

Adding a couple of tests would be amazing 👍

If end-to-end tests are difficult to craft, at least testing the core functions like those copying files to make sure they are correct would go a long way!

[chicoxyzzy]

Ok, I think it's ready. I've also created a templates repo, please review it: https://github.com/dispatchrun/dispatch-templates

[vadimdemedes]

"dispatch init will try to get the SHA of the latest commit from the repository and compare it to local SHA. If values differ, Dispatch CLI will propose user to update templates first."

Can we skip the question about updating templates and do it transparently to the user?

[chicoxyzzy]

Yes, let's do it 👍

[achille-roussel]

Looks like there's a test that's failing when I run it 🤔

$ make test
go build -o build/darwin/arm64/dispatch .
go test ./...
?   	github.com/dispatchrun/dispatch	[no test files]
--- FAIL: TestRunCommand (0.34s)
    --- FAIL: TestRunCommand/Run_with_env_variable_in_local_env_vars_has_priority_over_the_one_in_the_env_file (0.34s)
        run_test.go:125: Expected printenv in the output: 2024/07/03 16:25:28 INFO loading environment variables from file path=/var/folders/qc/zv1mt0j11sscgjygfx47nxlm0000gn/T/TestRunCommandRun_with_env_variable_in_local_env_vars_has_priority_over_the_one_in_the_env_file1550241151/001/test.env
            dispatch | 2024-07-03 16:25:28.027 starting session session_id=2tKgIdbajqVaIRM8ctdBcw

            Error: command 'printenv CHARACTER' exited unexpectedly
            Usage:
              dispatch run [flags]

            Flags:
              -e, --endpoint string   Host:port that the local application endpoint is listening on (default "127.0.0.1:8000")
              -h, --help              help for run
              -s, --session string    Optional session to resume
                  --verbose           Enable verbose logging

            Global Flags:
              -k, --api-key string    Dispatch API key (env: DISPATCH_API_KEY)
                  --env-file string   Path to .env file



FAIL
FAIL	github.com/dispatchrun/dispatch/cli	1.766s
FAIL
make: *** [test] Error 1

[achille-roussel]

I'm curious whether we could leave the current directly as-is instead of removing all the files:

~/go/src/github.com/dispatchrun/dispatch/build/darwin/arm64 $ ./dispatch init python
Directory . is not empty. Do you want to overwrite it? [y/N]
y
Template python was created in /Users/achilleroussel/go/src/github.com/dispatchrun/dispatch/build/darwin/arm64

Even if we ask the user, removing their files seems like a dangerous choice to make... mistakes happen easily.

Another alternative could be to simply refuse to initialize a template in a non-empty directory, then we don't need to prompt them either.

[chicoxyzzy]

Another alternative could be to simply refuse to initialize a template in a non-empty directory, then we don't need to prompt them either.

I agree. Fixed

[chicoxyzzy]

Looks like there's a test that's failing when I run it 🤔

Weird. This is a test for the dispatch run command. I don't think it's blocking for this PR, but I will take a look what's wrong here. It looks like printenv is not installed on your device / OS.

[achille-roussel]

It seems to be there:

$ which printenv
/usr/bin/printenv

I expect we would get a different error if the program wasn't found as well.

[achille-roussel]

Really nice work on this 👏

[chicoxyzzy]

I've created a separate issue for the failing test and other dispatch run improvements #80