Fix generate comment diff processor build failure (GoogleCloudPlatfor…

…m#10164)

* Refactored generate_comment to continue in the face of errors

Also switched to go template for comment formatting

* Moved to structured data for diffs

Also added error formatting into comment

* Added basic tests for comment formatting

* Skipped missing tests and breaking changes if repo failed to clone

* Force generation

* Breaking change

* Fixed error display in diff comment

* Marked diff-processor targets as not being real files

* Added PATH to diffProcessorEnv

* Fixed formatting for error sections

* Cleaned up passthrough env var usage

* Made exec.sh exit 1 if there are any errors running the magician

* Don't error on initial build of the magician binary

* Added missing  env var for diff processor build

* Force generation of tf-oics

* Revert "Force generation of tf-oics"

This reverts commit fcb65f1.

* Revert "Force generation"

This reverts commit 596d1eb.

* Revert "Breaking change"

This reverts commit fb04ad4.

* Force missing test run

* force missing tests to run - take 2

* Revert "force missing tests to run - take 2"

This reverts commit 34f7d16.

* Revert "Force missing test run"

This reverts commit 90e664a.

.ci/magician/cmd/DIFF_COMMENT.md

@@ -0,0 +1,36 @@
+Hi there, I'm the Modular magician. I've detected the following information about your changes:
+
+## Diff report
+{{ $diffsLength := len .Diffs }}{{if eq $diffsLength 0 }}
+Your PR hasn't generated any diffs, but I'll let you know if a future commit does.
+{{else}}
+Your PR generated some diffs in downstreams - here they are.
+
+{{range .Diffs -}}
+{{.Title}}: [Diff](https://github.com/modular-magician/{{.Repo}}/compare/auto-pr-{{$.PrNumber}}-old..auto-pr-{{$.PrNumber}}) ({{.DiffStats}})
+{{end -}}
+{{end -}}
+
+{{- $breakingChangesLength := len .BreakingChanges }}
+{{- if gt $breakingChangesLength 0}}
+## Breaking Change(s) Detected
+
+The following breaking change(s) were detected within your pull request.
+
+{{- range .BreakingChanges}}
+- {{.}}{{end}}
+
+If you believe this detection to be incorrect please raise the concern with your reviewer.
+If you intend to make this change you will need to wait for a [major release](https://www.terraform.io/plugin/sdkv2/best-practices/versioning#example-major-number-increments) window.
+An `override-breaking-change` label can be added to allow merging.
+{{end}}
+{{.MissingTests}}
+{{- $errorsLength := len .Errors}}
+{{- if gt $errorsLength 0}}
+## Errors
+{{range .Errors}}
+{{.Title}}:
+{{- range .Errors}}
+- {{.}}{{end}}
+{{end}}
+{{- end -}}