[Proposal] Transparent skaffold init

docs/design_proposals/transparent-init.md

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+# Transparent Init
+
+* Author(s): Marlon Gamez
+* Design Shepherd: \<skaffold-core-team-member\>
+* Date: 10/13/2020
+* Status: [Reviewed/Cancelled/Under implementation/Complete]
+
+## Background
+
+This proposal is brought about by an older issue, [#1273](https://github.com/GoogleContainerTools/skaffold/issues/1273)
+
+With the recent focus on skaffold UX, we've decided to see how we can improve the onboarding experience when using skaffold.
+One way we'd like to do this is by allowing the user to simply install skaffold and run any of the skaffold commands in their project, without having to first run `skaffold init` and go through the interactive portion of creating a config for their project.
+To do this, we'd like to automatically create a config upon invocation of skaffold commands, so that the user doesn't have to see something like this
+```
+❯ skaffold dev
+skaffold config file skaffold.yaml not found - check your current working directory, or try running `skaffold init`
+```
+when trying to run skaffold.
+
+## Design
+
+With transparent init, a user's first run of `skaffold dev` could look something like this:
+
+Given a simple project structure:
+```
+project-dir
+├── Dockerfile
+├── README.md
+├── k8s-pod.yaml
+└── main.go
+```
+Running skaffold dev:
+```
+❯ skaffold dev
+Skaffold config file not found. Generating temporary config for use this run.
+Listing files to watch...
+ - skaffold-example
+Generating tags...
+ - skaffold-example -> skaffold-example:v1.14.0-59-g7e5ae4cbc-dirty
+Checking cache...
+ - skaffold-example: Not found. Building
+Found [minikube] context, using local docker daemon.
+Building [skaffold-example]...
+Sending build context to Docker daemon  3.072kB
+...
+```
+
+There are two approaches to implementation that I've considered:
+
+**Creating a temporary `skaffold.yaml` by running `skaffold init --force`**
+
+Under the hood view:
+- `skaffold dev` is run
+- skaffold searches for a `skaffold.yaml` file in the directory, finds nothing
+- skaffold creates a new config using `skaffold init --force`
+- the new config is parsed and brought into memory
+- the config file is deleted from disk
+- `skaffold dev` continues like normal
+
+**Creating the config in memory using init functions**
+
+Under the hood view:
+- `skaffold dev` is run
+- skaffold searches for a `skaffold.yaml` file in the directory, finds nothing
+- skaffold creates a new config and keeps in memory
+- `skaffold dev` continues like normal
+
+## Open Issues/Questions
+
+**Should generation of the config all happen in memory? By refactoring `DoInit()` we could probably generate the config and start using it without having to write/read the `skaffold.yaml` from disk**
+
+*Unresolved*
+
+**Should we prompt the user to ask if they'd like to save this config for future use?**
+
+*Unresolved*
+
+**Should the config being used be printed to the terminal? Tradeoff of information vs clutter**
+
+*Unresolved*
+
+## Implementation plan
+
+If we decide upon the approach in which the `skaffold.yaml` is written to/read from disk, it would be pretty straightforward to implement this.
+
+If we decide to have the config exist only in memory, we may want to split this into a couple PRs. Maybe something like this:
+1. Refactor `DoInit()` so that it is broken into parts that we can use later
+2. User the new parts to implement the automatic generation of the config
+
+
+## Integration test plan
+
+New integration tests can be added to check that invocations of skaffold commands in folders without a skaffold config still run properly. With the other plans to change skaffold init, these will have to be updated as well.