ref: use git branch --show-current instead of sed (#2550)

Author: asottile-sentry

install/check-latest-commit.sh

@@ -2,7 +2,7 @@ echo "${_group}Checking for latest commit ... "
 
 # Checks if we are on latest commit from github if it is running from master branch
 if [[ -d "../.git" && "${SKIP_COMMIT_CHECK:-0}" != 1 ]]; then
-  if [[ $(git branch | sed -n '/\* /s///p') == "master" ]]; then
+  if [[ $(git branch --show-current) == "master" ]]; then
     if [[ $(git rev-parse HEAD) != $(git ls-remote $(git rev-parse --abbrev-ref @{u} | sed 's/\// /g') | cut -f1) ]]; then
       echo "Seems like you are not using the latest commit from the self-hosted repository. Please pull the latest changes and try again, or suppress this check with --skip-commit-check."
       exit 1