Added terraform-docs integration (#13)

* Add hook to create readme

* Updated README

.pre-commit-hooks.yaml

@@ -6,6 +6,14 @@
   files: (\.tf|\.tfvars)$
   exclude: \.terraform\/.*$
 
+- id: terraform_docs
+  name: Terraform Docs
+  description: Inserts input and output documentation into README.md (using terraform-docs).
+  entry: terraform_docs.sh
+  language: script
+  files: (\.tf)$
+  exclude: \.terraform\/.*$
+
 - id: terraform_validate_no_variables
   name: Terraform validate without variables
   description: Validates all Terraform configuration files without checking whether all required variables were set (basic check).

README.md

@@ -6,16 +6,24 @@ Several [pre-commit](http://pre-commit.com/) hooks to keep Terraform configurati
 * `terraform_fmt` - Rewrites all Terraform configuration files to a canonical format.
 * `terraform_validate_no_variables` - Validates all Terraform configuration files without checking whether all required variables were set.
 * `terraform_validate_with_variables` - Validates all Terraform configuration files and checks whether all required variables were specified.
+* `terraform_docs` - Inserts input and output documentation into `README.md`.
 
-Note that `terraform_validate_no_variables` and `terraform_validate_with_variables` will not work if variables are being set dynamically (eg, when using [Terragrunt](https://github.com/gruntwork-io/terragrunt)). Use `terragrunt validate` command instead.
+## Notes about hooks
 
-An example `.pre-commit-config.yaml`:
+1. `terraform_validate_no_variables` and `terraform_validate_with_variables` will not work if variables are being set dynamically (eg, when using [Terragrunt](https://github.com/gruntwork-io/terragrunt)). Use `terragrunt validate` command instead.
+
+1. `terraform_docs` will insert/update documentation generated by [terraform-docs](https://github.com/segmentio/terraform-docs) between markers - `<!-- BEGINNING OF PRE-COMMIT-TERRAFORM DOCS HOOK -->` and `<!-- END OF PRE-COMMIT-TERRAFORM DOCS HOOK -->` if they are present in `README.md`. Make sure that `terraform-docs` is installed.
+
+## Example
+
+`.pre-commit-config.yaml`:
 
 ```yaml
 - repo: git://github.com/antonbabenko/pre-commit-terraform
-  sha: v1.6.0
+  rev: v1.7.0
   hooks:
     - id: terraform_fmt
+    - id: terraform_docs
 ```
 
-Enjoy the clean code!
+Enjoy the clean and documented code!

hooks.yaml

@@ -6,6 +6,14 @@
   files: (\.tf|\.tfvars)$
   exclude: \.terraform\/.*$
 
+- id: terraform_docs
+  name: Terraform Docs
+  description: Inserts input and output documentation into README.md (using terraform-docs).
+  entry: terraform_docs.sh
+  language: script
+  files: (\.tf)$
+  exclude: \.terraform\/.*$
+
 - id: terraform_validate_no_variables
   name: Terraform validate without variables
   description: Validates all Terraform configuration files without checking whether all required variables were set (basic check).

terraform_docs.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+set -e
+
+declare -a paths
+declare -a tfvars_files
+
+index=0
+
+for file_with_path in "$@"; do
+  file_with_path="${file_with_path// /__REPLACED__SPACE__}"
+
+  paths[index]=$(dirname "$file_with_path")
+
+  if [[ "$file_with_path" == *".tfvars" ]]; then
+    tfvars_files+=("$file_with_path")
+  fi
+
+  let "index+=1"
+done
+
+readonly tmp_file="tmp_$(date | md5).txt"
+
+for path_uniq in $(echo "${paths[*]}" | tr ' ' '\n' | sort -u); do
+  path_uniq="${path_uniq//__REPLACED__SPACE__/ }"
+
+  pushd "$path_uniq" > /dev/null
+
+  terraform-docs md ./ > "$tmp_file"
+
+  # Replace content between markers with the placeholder - http://fahdshariff.blogspot.no/2012/12/sed-mutli-line-replacement-between-two.html
+  sed -i -n '/BEGINNING OF PRE-COMMIT-TERRAFORM DOCS HOOK/{p;:a;N;/END OF PRE-COMMIT-TERRAFORM DOCS HOOK/!ba;s/.*\n/I_WANT_TO_BE_REPLACED\n/};p' README.md
+
+  # Replace placeholder with the content of the file - https://stackoverflow.com/a/31057013/550451
+  sed -i -e "/I_WANT_TO_BE_REPLACED/r $tmp_file" -e "//d" README.md
+
+  rm -f "$tmp_file"
+
+  popd > /dev/null
+done