fix: add checks and handle errors brew-bump.sh

feat(script): add steps-lib, is_env_var_set & test

feat(brew-bump): add check for VERSION

feat(brew-bump): check HOMEBREW_GITHUB_API_TOKEN

feat(steps-lib): add directory_exists helper fn

fix(brew-bump): check that git clone worked

feat(brew-bump): add check for remote upstream

fix: remove upstream command thing

feat(steps-lib): add file_exists helper function

feat(brew-bump): add check for git-askpass.sh

feat(steps-lib): add is_executable function & test

feat(brew-bump): add check for is_executable

refactor: use GIT_ASKPASS as variable

test/scripts/steps-lib.bats

@@ -0,0 +1,46 @@
+#!/usr/bin/env bats
+
+SCRIPT_NAME="steps-lib.sh"
+SCRIPT="$BATS_TEST_DIRNAME/../../ci/steps/$SCRIPT_NAME"
+
+source "$SCRIPT"
+
+@test "is_env_var_set should return 1 if env var is not set" {
+  run is_env_var_set "ASDF_TEST_SET"
+  [ "$output" = 1 ]
+}
+
+@test "is_env_var_set should return 0 if env var is set" {
+  ASDF_TEST_SET="test" run is_env_var_set "ASDF_TEST_SET"
+  [ "$output" = 0 ]
+}
+
+@test "directory_exists should 1 if directory doesn't exist" {
+  run directory_exists "/tmp/asdfasdfasdf"
+  [ "$output" = 1 ]
+}
+
+@test "directory_exists should 0 if directory exists" {
+  run directory_exists "$(pwd)"
+  [ "$output" = 0 ]
+}
+
+@test "file_exists should 1 if file doesn't exist" {
+  run file_exists "hello-asfd.sh"
+  [ "$output" = 1 ]
+}
+
+@test "file_exists should 0 if file exists" {
+  run file_exists "$SCRIPT"
+  [ "$output" = 0 ]
+}
+
+@test "is_executable should 1 if file isn't executable" {
+  run is_executable "hello-asfd.sh"
+  [ "$output" = 1 ]
+}
+
+@test "is_executable should 0 if file is executable" {
+  run is_executable "$SCRIPT"
+  [ "$output" = 0 ]
+}