Implement support for CI variables of type file

Add env_var and file as supported types for CI variables. Variables of
type file expose to users existing gitlab-runner behaviour - save
variable value into a temp file and set the path to this file in an ENV
var named after the variable key.

Resolves https://gitlab.com/gitlab-org/gitlab-ce/issues/46806.

4 files changed, 45 insertions, 25 deletions

diff --git a/doc/api/group_level_variables.md b/doc/api/group_level_variables.md
index 3551bfa3f8b..7b00df6d775 100644
--- a/doc/api/group_level_variables.md
+++ b/doc/api/group_level_variables.md
@@ -22,10 +22,12 @@ curl --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/a
 [
     {
         "key": "TEST_VARIABLE_1",
+        "variable_type": "env_var",
         "value": "TEST_1"
     },
     {
         "key": "TEST_VARIABLE_2",
+        "variable_type": "env_var",
         "value": "TEST_2"
     }
 ]
@@ -51,6 +53,7 @@ curl --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/a
 ```json
 {
     "key": "TEST_VARIABLE_1",
+    "variable_type": "env_var",
     "value": "TEST_1"
 }
 ```
@@ -63,12 +66,13 @@ Create a new variable.
 POST /groups/:id/variables
 ```
 
-| Attribute   | Type    | required | Description           |
-|-------------|---------|----------|-----------------------|
-| `id`        | integer/string | yes      | The ID of a group or [URL-encoded path of the group](README.md#namespaced-path-encoding) owned by the authenticated user   |
-| `key`       | string  | yes      | The `key` of a variable; must have no more than 255 characters; only `A-Z`, `a-z`, `0-9`, and `_` are allowed |
-| `value`     | string  | yes      | The `value` of a variable |
-| `protected` | boolean | no       | Whether the variable is protected |
+| Attribute       | Type    | required | Description           |
+|-----------------|---------|----------|-----------------------|
+| `id`            | integer/string | yes      | The ID of a group or [URL-encoded path of the group](README.md#namespaced-path-encoding) owned by the authenticated user   |
+| `key`           | string  | yes      | The `key` of a variable; must have no more than 255 characters; only `A-Z`, `a-z`, `0-9`, and `_` are allowed |
+| `value`         | string  | yes      | The `value` of a variable |
+| `variable_type` | string  | no       | The type of a variable. Available types are: `env_var` (default) and `file` |
+| `protected`     | boolean | no       | Whether the variable is protected |
 
 ```
 curl --request POST --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/api/v4/groups/1/variables" --form "key=NEW_VARIABLE" --form "value=new value"
@@ -78,6 +82,7 @@ curl --request POST --header "PRIVATE-TOKEN: <your_access_token>" "https://gitla
 {
     "key": "NEW_VARIABLE",
     "value": "new value",
+    "variable_type": "env_var",
     "protected": false
 }
 ```
@@ -90,12 +95,13 @@ Update a group's variable.
 PUT /groups/:id/variables/:key
 ```
 
-| Attribute   | Type    | required | Description             |
-|-------------|---------|----------|-------------------------|
-| `id`        | integer/string | yes      | The ID of a group or [URL-encoded path of the group](README.md#namespaced-path-encoding) owned by the authenticated user     |
-| `key`       | string  | yes      | The `key` of a variable   |
-| `value`     | string  | yes      | The `value` of a variable |
-| `protected` | boolean | no       | Whether the variable is protected |
+| Attribute       | Type    | required | Description             |
+|-----------------|---------|----------|-------------------------|
+| `id`            | integer/string | yes      | The ID of a group or [URL-encoded path of the group](README.md#namespaced-path-encoding) owned by the authenticated user     |
+| `key`           | string  | yes      | The `key` of a variable   |
+| `value`         | string  | yes      | The `value` of a variable |
+| `variable_type` | string  | no       | The type of a variable. Available types are: `env_var` (default) and `file` |
+| `protected`     | boolean | no       | Whether the variable is protected |
 
 ```
 curl --request PUT --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/api/v4/groups/1/variables/NEW_VARIABLE" --form "value=updated value"
@@ -105,6 +111,7 @@ curl --request PUT --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab
 {
     "key": "NEW_VARIABLE",
     "value": "updated value",
+    "variable_type": "env_var",
     "protected": true
 }
 ```
diff --git a/doc/api/pipeline_schedules.md b/doc/api/pipeline_schedules.md
index 50d9e007ecc..470e55425f8 100644
--- a/doc/api/pipeline_schedules.md
+++ b/doc/api/pipeline_schedules.md
@@ -88,6 +88,7 @@ curl --header "PRIVATE-TOKEN: k5ESFgWY2Qf5xEvDcFxZ" "https://gitlab.example.com/
     "variables": [
         {
             "key": "TEST_VARIABLE_1",
+            "variable_type": "env_var",
             "value": "TEST_1"
         }
     ]
@@ -296,6 +297,7 @@ POST /projects/:id/pipeline_schedules/:pipeline_schedule_id/variables
 | `pipeline_schedule_id` | integer        | yes      | The pipeline schedule id |
 | `key`                  | string         | yes      | The `key` of a variable; must have no more than 255 characters; only `A-Z`, `a-z`, `0-9`, and `_` are allowed |
 | `value`                | string         | yes      | The `value` of a variable |
+| `variable_type`        | string         | no       | The type of a variable. Available types are: `env_var` (default) and `file` |
 
 ```sh
 curl --request POST --header "PRIVATE-TOKEN: k5ESFgWY2Qf5xEvDcFxZ" --form "key=NEW_VARIABLE" --form "value=new value" "https://gitlab.example.com/api/v4/projects/29/pipeline_schedules/13/variables"
@@ -304,6 +306,7 @@ curl --request POST --header "PRIVATE-TOKEN: k5ESFgWY2Qf5xEvDcFxZ" --form "key=N
 ```json
 {
     "key": "NEW_VARIABLE",
+    "variable_type": "env_var",
     "value": "new value"
 }
 ```
@@ -322,6 +325,7 @@ PUT /projects/:id/pipeline_schedules/:pipeline_schedule_id/variables/:key
 | `pipeline_schedule_id` | integer        | yes      | The pipeline schedule id |
 | `key`                  | string         | yes      | The `key` of a variable   |
 | `value`                | string         | yes      | The `value` of a variable |
+| `variable_type`        | string         | no       | The type of a variable. Available types are: `env_var` (default) and `file` |
 
 ```sh
 curl --request PUT --header "PRIVATE-TOKEN: k5ESFgWY2Qf5xEvDcFxZ" --form "value=updated value" "https://gitlab.example.com/api/v4/projects/29/pipeline_schedules/13/variables/NEW_VARIABLE"
@@ -331,6 +335,7 @@ curl --request PUT --header "PRIVATE-TOKEN: k5ESFgWY2Qf5xEvDcFxZ" --form "value=
 {
     "key": "NEW_VARIABLE",
     "value": "updated value"
+    "variable_type": "env_var",
 }
 ```
 
diff --git a/doc/api/pipelines.md b/doc/api/pipelines.md
index 1a4310ef328..753faec3cc8 100644
--- a/doc/api/pipelines.md
+++ b/doc/api/pipelines.md
@@ -114,6 +114,7 @@ Example of response
 [
   {
     "key": "RUN_NIGHTLY_BUILD",
+    "variable_type": "env_var",
     "value": "true"
   },
   {
@@ -135,7 +136,7 @@ POST /projects/:id/pipeline
 |------------|---------|----------|---------------------|
 | `id`       | integer/string | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user |
 | `ref`       | string | yes      | Reference to commit |
-| `variables` | array | no | An array containing the variables available in the pipeline, matching the structure [{ 'key' => 'UPLOAD_TO_S3', 'value' => 'true' }] |
+| `variables` | array | no | An array containing the variables available in the pipeline, matching the structure [{ 'key' => 'UPLOAD_TO_S3', 'variable_type' => 'file', 'value' => 'true' }] |
 
 ```
 curl --request POST --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/api/v4/projects/1/pipeline?ref=master"
diff --git a/doc/api/project_level_variables.md b/doc/api/project_level_variables.md
index 438bebe62f5..4a6f5624394 100644
--- a/doc/api/project_level_variables.md
+++ b/doc/api/project_level_variables.md
@@ -20,10 +20,12 @@ curl --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/a
 [
     {
         "key": "TEST_VARIABLE_1",
+        "variable_type": "env_var",
         "value": "TEST_1"
     },
     {
         "key": "TEST_VARIABLE_2",
+        "variable_type": "env_var",
         "value": "TEST_2"
     }
 ]
@@ -49,6 +51,7 @@ curl --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/a
 ```json
 {
     "key": "TEST_VARIABLE_1",
+    "variable_type": "env_var",
     "value": "TEST_1"
 }
 ```
@@ -61,12 +64,13 @@ Create a new variable.
 POST /projects/:id/variables
 ```
 
-| Attribute   | Type    | required | Description           |
-|-------------|---------|----------|-----------------------|
-| `id`        | integer/string | yes      | The ID of a project or [urlencoded NAMESPACE/PROJECT_NAME of the project](README.md#namespaced-path-encoding) owned by the authenticated user   |
-| `key`       | string  | yes      | The `key` of a variable; must have no more than 255 characters; only `A-Z`, `a-z`, `0-9`, and `_` are allowed |
-| `value`     | string  | yes      | The `value` of a variable |
-| `protected` | boolean | no       | Whether the variable is protected |
+| Attribute       | Type    | required | Description           |
+|-----------------|---------|----------|-----------------------|
+| `id`            | integer/string | yes      | The ID of a project or [urlencoded NAMESPACE/PROJECT_NAME of the project](README.md#namespaced-path-encoding) owned by the authenticated user   |
+| `key`           | string  | yes      | The `key` of a variable; must have no more than 255 characters; only `A-Z`, `a-z`, `0-9`, and `_` are allowed |
+| `value`         | string  | yes      | The `value` of a variable |
+| `variable_type` | string  | no       | The type of a variable. Available types are: `env_var` (default) and `file` |
+| `protected`     | boolean | no       | Whether the variable is protected |
 
 ```
 curl --request POST --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/api/v4/projects/1/variables" --form "key=NEW_VARIABLE" --form "value=new value"
@@ -76,6 +80,7 @@ curl --request POST --header "PRIVATE-TOKEN: <your_access_token>" "https://gitla
 {
     "key": "NEW_VARIABLE",
     "value": "new value",
+    "variable_type": "env_var",
     "protected": false
 }
 ```
@@ -88,12 +93,13 @@ Update a project's variable.
 PUT /projects/:id/variables/:key
 ```
 
-| Attribute   | Type    | required | Description             |
-|-------------|---------|----------|-------------------------|
-| `id`        | integer/string | yes      | The ID of a project or [urlencoded NAMESPACE/PROJECT_NAME of the project](README.md#namespaced-path-encoding) owned by the authenticated user     |
-| `key`       | string  | yes      | The `key` of a variable   |
-| `value`     | string  | yes      | The `value` of a variable |
-| `protected` | boolean | no       | Whether the variable is protected |
+| Attribute       | Type    | required | Description             |
+|-----------------|---------|----------|-------------------------|
+| `id`            | integer/string | yes      | The ID of a project or [urlencoded NAMESPACE/PROJECT_NAME of the project](README.md#namespaced-path-encoding) owned by the authenticated user     |
+| `key`           | string  | yes      | The `key` of a variable   |
+| `value`         | string  | yes      | The `value` of a variable |
+| `variable_type` | string  | no       | The type of a variable. Available types are: `env_var` (default) and `file` |
+| `protected`     | boolean | no       | Whether the variable is protected |
 
 ```
 curl --request PUT --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/api/v4/projects/1/variables/NEW_VARIABLE" --form "value=updated value"
@@ -103,6 +109,7 @@ curl --request PUT --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab
 {
     "key": "NEW_VARIABLE",
     "value": "updated value",
+    "variable_type": "env_var",
     "protected": true
 }
 ```