Exposes a `--log-level` arg on every command
Replaces all `log` uses with either `fmt.Fprint(os.Stderr)` or zerolog calls

Benefits:
- Rather than mixing actual logs (that should have a level) and things that we want to print to stderr, using zerolog and fmt is more deliberate in meaning
- Logs can be disabled or turned on using the `--log-level` option
- We'll be able to add more verbose logs without potentially annoying people. An example is the "Loading environment" messages that the export command now prints. I shifted that to debug
- Will allow for trace level logs. Ex: #751, logs from the underlying `kubectl` exec or helm

Follow-up to #766
- Shift linting name logging to debug logging. Instead of sending everything to stdout, we can now have a cleaner "report"
- Missed some `log.Printf`(alias for Debug) in helm code, shifted that to info logs
- Added some caching logs, whether or not it's a cache hit + time elasped to calculate hash
- Changed `time` for `duration_ms` in env loading log. This conflicts with the log time

* Replace external call to `diffstat` with native code
Closes #767

`diffstat` is not available in the `apk` registry so we would have to compile it manually to add it to the docker image

Parsing a diff to get the number of lines is pretty simple

I tried a few external libraries but they didn't work right + less libs is better

* Add docstring

* Add new `tk tool importers` command

This command is powerful when used with the `--merge-strategy=replace-envs` flag added here: #760

Given a repository with a large number of Tanka environments, exporting the whole set can be very time consuming if done on every commit.
What a user probably wants to do is to only export the environments that have changed.
To do this, we need to actually find out what files affect which environments, and this is what this new command does.
A user can now pass the list of files modified in a git commit, and run `tk export` on the set of environments affected by those files.

* Add comments and simplify functions

When an error occurs, it is ultimately brought to the `main.go` file where it is printed for the user (or machine)
Using log.Fatal garbles the error by not rendering newlines

This reverts #774 but adds an os.Exit(1) which is an alternative fix to what the PR did

I hadn't done it before because the benefit was minimal. However, I've found out that for very heavily used libraries (used by hundreds/thousands of files), it does help
For example, for [`ksonnet-util`](https://github.com/grafana/jsonnet-libs/tree/master/ksonnet-util) which we use everywhere, compute time goes from ~13s to ~6s

Signed-off-by: Jordi Clariana <[email protected]>

Signed-off-by: Jordi Clariana <[email protected]>

Also, the `--prune` option for vendoring
Closes #778

To know that a resource should be pruned, we check that it has a field manager of a known tool
However, Flux applies with the `kustomize-controller` field manager, which isn't in the list
Therefore, a `diff --with-prune` doesn't detect resources applied with Flux V2

Also: Added more logs to the `Orphaned` function. It now lists all resources on debug mode

* Find Importers: Add missing `break` in relative paths logic

Jsonnet is weird with relative paths
Given two envs in their own folder. The two following imports in `env1/main.jsonnet will work`: `../env2/main.jsonnet` and `../../env2/main.jsonnet`, so we have to try all of them

The logic does so in a loop. Without a `break`, the logic worked when the match was found on the first case (and correct one) but failed on the second

* Simpler logic + add test

* Add new test

This gets rid of netlify which we don't really need and is blocking PRs like #783
This contains two different parts:
- A step that deploys to a preview for PRs
- A step that deploys on a push to main

* chore(jsonnet): update to 0.19.0

* Bump version to v0.19.1

* Do not use std.member (google/go-jsonnet#656)

Co-authored-by: Salva Corts <[email protected]>

When DNS is setup in Github pages, the URLs (ex: https://grafana.github.io/tanka/pr-preview/pr-783/) now always redirect to the tanka.dev DNS name
So it becomes: https://tanka.dev/pr-preview/pr-783/
Therefore, the path prefix is now wrong

Everything else is now running fine without Netlify!

Signed-off-by: Justin Lei <[email protected]>

Signed-off-by: Justin Lei <[email protected]>

* Support forcing color output on/off

Closes #798

Introduce flag `--color` to control the colorization of diff output.

Add flag to all commands that can output colorized diff text:
- `diff`
- `apply`
- `prune`

`--color` has 3 allowed values:
- `auto` (default): colorize if stdout is a tty (current behavior)
- `always`: always colorize output
- `never`: never colorize output

* Remove unused attribute

Co-authored-by: Matt Wilder <[email protected]>
Co-authored-by: Julien Duchesne <[email protected]>