Add direnv support with boilerplate

This add a .envrc file that will be used by direnv to setup the
environment for the project if `direnv` is enabled. It also adds a
`.env.sample` to give an example of what it could be useful for.
And it adds `.env` to gitignore to make sure people do not commit
their specific environment configurations.

Signed-off-by: Vincent Demeester <vdemeest@redhat.com>

.env.sample

@@ -0,0 +1,4 @@
+# shellcheck shell=bash
+# This is an example of a .env file
+export GOMAXPROCS=6
+export KO_DOCKER_REPO=gcr.io/tektoncd/pipeline

.envrc

@@ -0,0 +1,18 @@
+# shellcheck shell=bash
+
+# If .env missing; restore from .env.sample and validate
+# See https://github.com/direnv/direnv/wiki/.envrc-Boilerplate
+if [[ -f .env.sample ]]; then
+  if [[ ! -f .env ]]; then
+    if ! command -v createnv > /dev/null; then
+      echo 'WARN|Createnv missing; try: pyenv local 3.x && pip install createnv'
+    else
+      createnv --use-default --overwrite || echo 'ERROR|https://github.com/cuducos/createnv'
+      if command dotenv-linter --version >&/dev/null; then
+        dotenv-linter .env || echo 'ERROR|https://dotenv-linter.github.io'
+      fi
+    fi
+  fi
+fi
+
+dotenv_if_exists || direnv status # https://direnv.net/man/direnv-stdlib.1.html

.gitignore

@@ -60,3 +60,6 @@ test/pullrequest/pullrequest-init
 
 # Backup of API reference docs generated by sed
 docs/pipeline-api.md.backup
+
+# Ignore .env files
+/.env