set the remote for git checkout

Summary:
This will fix the error: "error: pathspec '2.2.fb.branch' did not match any file(s) known to git."

Tested by manually sshing to sandcastle and running the command.
Closes https://github.com/facebook/rocksdb/pull/2599

Differential Revision: D5441130

Pulled By: maysamyabandeh

fbshipit-source-id: a22fd6a52221471bafbba8990394b499535e5812

tools/check_format_compatible.sh

@@ -76,7 +76,7 @@ https_proxy="fwdproxy:8080" git fetch github_origin
 for checkout_obj in "${checkout_objs[@]}"
 do
    echo == Generating DB from "$checkout_obj" ...
-   git checkout $checkout_obj
+   https_proxy="fwdproxy:8080" git checkout github_origin/$checkout_obj -b $checkout_obj
    make clean
    make ldb -j32
    generate_db $input_data_path $test_dir/$checkout_obj
@@ -85,7 +85,7 @@ done
 checkout_flag=${1:-"master"}
 
 echo == Building $checkout_flag debug
-git checkout $checkout_flag
+https_proxy="fwdproxy:8080" git checkout github_origin/$checkout_flag -b $checkout_flag
 make clean
 make ldb -j32
 compare_base_db_dir=$test_dir"/base_db_dir"
@@ -101,7 +101,7 @@ done
 for checkout_obj in "${forward_compatible_checkout_objs[@]}"
 do
    echo == Build "$checkout_obj" and try to open DB generated using $checkout_flag...
-   git checkout $checkout_obj
+   https_proxy="fwdproxy:8080" git checkout github_origin/$checkout_obj -b $checkout_obj
    make clean
    make ldb -j32
    compare_db $test_dir/$checkout_obj $compare_base_db_dir forward_${checkout_obj}_dump.txt 0