Document CIRRUS_CLONE_SUBMODULES (#830)

* Document CIRRUS_CLONE_SUBMODULES

* .spelling: add CIRRUS_CLONE_SUBMODULES and submodules

* .spelling: sort entries

.spelling

@@ -12,7 +12,6 @@ Bundler
 CCMenu
 CCTray
 CI
-CIs
 CIRRUS_API_CREATED
 CIRRUS_BASE_BRANCH
 CIRRUS_BASE_SHA
@@ -23,6 +22,7 @@ CIRRUS_CHANGE_MESSAGE
 CIRRUS_CHANGE_TITLE
 CIRRUS_CI
 CIRRUS_CLONE_DEPTH
+CIRRUS_CLONE_SUBMODULES
 CIRRUS_CRON
 CIRRUS_DEFAULT_BRANCH
 CIRRUS_HTTP_CACHE_HOST
@@ -48,6 +48,7 @@ CIRRUS_WORKING_DIR
 CI_NODE_INDEX
 CI_NODE_TOTAL
 CIaaS
+CIs
 CONTINUOUS_INTEGRATION
 CPU
 CPUs
@@ -59,11 +60,11 @@ Dockerfiles
 Erlang
 FreeBSD
 GB
+GITHUB_CHECK_SUITE_ID
 GPU
 GPUs
 Gb
 GitHub
-GITHUB_CHECK_SUITE_ID
 Golang
 GolangCI
 Google
@@ -72,11 +73,11 @@ Heroku
 Homebrew
 Hypervisor
 IPs
-JetBrains
 JUnit
+JetBrains
+KVM-enabled
 Kaniko
 Kubernetes
-KVM-enabled
 Lifecycle
 MacStadium
 Makisu
@@ -91,14 +92,19 @@ Parallelization
 PowerShell
 Preemptible
 PyPI
+Qodana
+RSpec
 ReadMe
-Skaffold
+RuboCop
 SSDs
+Skaffold
+Unittest
 VMs
 Veertu
 WebHooks
 Webhooks
 Windows
+XCLogParser
 Xcode
 Zero-config
 autoscaler
@@ -134,14 +140,16 @@ git
 go-git
 gradle
 hostname
-invalidations
 iOS
+invalidations
 lifecycle
 macOS
+machine-parsable
 macstadium.community.nat.cirrus
 mimetype
 mimetypes
 namespace
+natively
 node
 nondeterministic
 nonintuitive
@@ -160,21 +168,15 @@ safelisting
 sh
 sharding
 stateful
+submodules
 support@cirruslabs.org
 sweat_smile
 timestamp
 unary
-Unittest
 vCPU
 vCPUs
+virtualization
 webhook
 white_check_mark
-virtualization
 x
 yarn
-RSpec
-RuboCop
-natively
-machine-parsable
-Qodana
-XCLogParser

docs/guide/writing-tasks.md

@@ -422,6 +422,7 @@ And some environment variables can be set to control behavior of the Cirrus CI A
 Name | Default Value | Description
 ---  | --- | ---
 CIRRUS_CLONE_DEPTH | `0` which will reflect in a full clone of a single branch | Clone depth.
+CIRRUS_CLONE_SUBMODULES | `false` | Set to `true` to clone submodules recursively.
 CIRRUS_LOG_TIMESTAMP | `false` | Indicate Cirrus Agent to prepend timestamp to each line of logs.
 CIRRUS_SHELL | `sh` on Linux/macOS/FreeBSD and `cmd.exe` on Windows. Set to `direct` to execute each script directly without wrapping the commands in a shell script. | Shell that Cirrus CI uses to execute scripts. By default `sh` is used.
 CIRRUS_WORKING_DIR | `cirrus-ci-build` folder inside of a system's temporary folder | Working directory where Cirrus CI executes builds. Default to `cirrus-ci-build` folder inside of a system's temporary folder.