checkout local branch in check_format_compatible.sh

Summary:
For forward_compatible_checkout_objs the local branch is already created in previous step. This patch avoid recreating it. This should address "fatal: A branch named '3.10.fb' already exists." errors.
Closes https://github.com/facebook/rocksdb/pull/2606

Differential Revision: D5443786

Pulled By: maysamyabandeh

fbshipit-source-id: 69d5a67b87677429cf36e3a467bd114d341f3b9c

tools/check_format_compatible.sh

@@ -41,8 +41,9 @@ with open('${input_data[$i]}', 'w') as f:
 EOF
 done
 
-declare -a checkout_objs=("2.2.fb.branch" "2.3.fb.branch" "2.4.fb.branch" "2.5.fb.branch" "2.6.fb.branch" "2.7.fb.branch" "2.8.1.fb" "3.0.fb.branch" "3.1.fb" "3.2.fb" "3.3.fb" "3.4.fb" "3.5.fb" "3.6.fb" "3.7.fb" "3.8.fb" "3.9.fb" "3.10.fb" "3.11.fb" "3.12.fb" "3.13.fb" "4.0.fb" "4.1.fb" "4.2.fb" "4.3.fb" "4.4.fb" "4.5.fb" "4.6.fb" "4.7.fb" "4.8.fb" "4.9.fb" "4.10.fb" "4.11.fb" "4.12.fb" "4.13.fb" "5.0.fb" "5.1.fb" "5.2.fb" "5.3.fb" "5.4.fb" "5.5.fb" "5.6.fb")
+declare -a backward_compatible_checkout_objs=("2.2.fb.branch" "2.3.fb.branch" "2.4.fb.branch" "2.5.fb.branch" "2.6.fb.branch" "2.7.fb.branch" "2.8.1.fb" "3.0.fb.branch" "3.1.fb" "3.2.fb" "3.3.fb" "3.4.fb" "3.5.fb" "3.6.fb" "3.7.fb" "3.8.fb" "3.9.fb")
 declare -a forward_compatible_checkout_objs=("3.10.fb" "3.11.fb" "3.12.fb" "3.13.fb" "4.0.fb" "4.1.fb" "4.2.fb" "4.3.fb" "4.4.fb" "4.5.fb" "4.6.fb" "4.7.fb" "4.8.fb" "4.9.fb" "4.10.fb" "4.11.fb" "4.12.fb" "4.13.fb" "5.0.fb" "5.1.fb" "5.2.fb" "5.3.fb" "5.4.fb" "5.5.fb" "5.6.fb")
+declare -a checkout_objs=(${backward_compatible_checkout_objs[@]} ${forward_compatible_checkout_objs[@]})
 
 generate_db()
 {
@@ -101,7 +102,7 @@ done
 for checkout_obj in "${forward_compatible_checkout_objs[@]}"
 do
    echo == Build "$checkout_obj" and try to open DB generated using $checkout_flag...
-   https_proxy="fwdproxy:8080" git checkout github_origin/$checkout_obj -b $checkout_obj
+   git checkout $checkout_obj
    make clean
    make ldb -j32
    compare_db $test_dir/$checkout_obj $compare_base_db_dir forward_${checkout_obj}_dump.txt 0