tests: run mvdan/shfmt on test runs

While I do not agree with _every_ style change, this will force Dokku to have consistent formatting across all shell scripts, which is arguably a Good Thing™.

The command used to reprocess everything is:

```shell
shfmt -l -bn -ci -i 2 -w .
```

plugins/git/subcommands/default

@@ -1,5 +1,6 @@
 #!/usr/bin/env bash
-set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+set -eo pipefail
+[[ $DOKKU_TRACE ]] && set -x
 source "$PLUGIN_AVAILABLE_PATH/git/internal-functions"
 
 cmd-git-help "git:help"

plugins/git/subcommands/initialize

@@ -1,11 +1,13 @@
 #!/usr/bin/env bash
 source "$PLUGIN_CORE_AVAILABLE_PATH/common/functions"
 source "$PLUGIN_AVAILABLE_PATH/git/functions"
-set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+set -eo pipefail
+[[ $DOKKU_TRACE ]] && set -x
 
 git-initialize-cmd() {
   declare desc="initialize a git repository for an app"
-  local cmd="git:initialize" argv=("$@"); [[ ${argv[0]} == "$cmd" ]] && shift 1
+  local cmd="git:initialize" argv=("$@")
+  [[ ${argv[0]} == "$cmd" ]] && shift 1
   declare APP="$1"
   is_valid_app_name "$APP"
 

plugins/git/subcommands/report

@@ -1,5 +1,6 @@
 #!/usr/bin/env bash
 source "$PLUGIN_AVAILABLE_PATH/git/internal-functions"
-set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+set -eo pipefail
+[[ $DOKKU_TRACE ]] && set -x
 
 cmd-git-report "$@"

plugins/git/subcommands/set

@@ -1,7 +1,8 @@
 #!/usr/bin/env bash
 source "$PLUGIN_CORE_AVAILABLE_PATH/common/functions"
 source "$PLUGIN_CORE_AVAILABLE_PATH/common/property-functions"
-set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+set -eo pipefail
+[[ $DOKKU_TRACE ]] && set -x
 
 fn-in-array() {
   declare desc="return true if value ($1) is in list (all other arguments)"
@@ -15,7 +16,8 @@ fn-in-array() {
 
 git-set-cmd() {
   declare desc="set or clear a git property for an app"
-  local cmd="git:set" argv=("$@"); [[ ${argv[0]} == "$cmd" ]] && shift 1
+  local cmd="git:set" argv=("$@")
+  [[ ${argv[0]} == "$cmd" ]] && shift 1
   declare APP="$1" KEY="$2" VALUE="$3"
   local VALID_KEYS=("deploy-branch" "rev-env-var")
   [[ -z "$APP" ]] && dokku_log_fail "Please specify an app to run the command on"