ci: use git fetch; remove submodule strategy from specific places

.gitlab-ci.yml

@@ -1,4 +1,8 @@
 variables:
+  # Using git fetch is faster.
+  # See https://docs.gitlab.com/ce/user/project/pipelines/settings.html#git-strategy
+  GIT_STRATEGY: "fetch"
+
   # Init submodules.
   # See https://docs.gitlab.com/ee/ci/yaml/#git-submodule-strategy
   GIT_SUBMODULE_STRATEGY: "recursive"

ci/core.yml

@@ -39,8 +39,6 @@ build core unix frozen:
 
 test core unix unit:
   stage: test
-  variables:
-    GIT_SUBMODULE_STRATEGY: none  # no need to fetch submodules
   dependencies:
     - build core unix frozen
   script:
@@ -49,8 +47,6 @@ test core unix unit:
 
 test core unix device:
   stage: test
-  variables:
-    GIT_SUBMODULE_STRATEGY: none  # no need to fetch submodules
   dependencies:
     - build core unix frozen
   script:
@@ -59,8 +55,6 @@ test core unix device:
 
 test core unix monero:
   stage: test
-  variables:
-    GIT_SUBMODULE_STRATEGY: none  # no need to fetch submodules
   dependencies:
     - build core unix frozen
   script:

ci/legacy.yml

@@ -47,8 +47,6 @@ build legacy emu:
 
 # TODO: aren't some tests from .travis.yml missing?
 test legacy emu:
-  variables:
-    GIT_SUBMODULE_STRATEGY: none  # no need to fetch submodules
   stage: test
   dependencies:
     - build legacy emu

ci/storage.yml

@@ -1,8 +1,6 @@
 image: registry.corp.sldev.cz/trezor/trezor-firmware/environment
 
 test storage:
-  variables:
-    GIT_SUBMODULE_STRATEGY: none  # no need to fetch submodules
   stage: test
   dependencies: []
   script: