create_source_tarball.sh: Use prerelease name from prerelease.txt when available instead of hard-coding "nightly"

Author: cameel

scripts/create_source_tarball.sh

@@ -8,12 +8,14 @@ source "${REPO_ROOT}/scripts/common.sh"
 cd "$REPO_ROOT"
 version=$(scripts/get_version.sh)
 commit_hash=$(git rev-parse --short=8 HEAD)
-commit_date=$(git show --format=%ci HEAD | head -n 1 | cut - -b1-10 | sed -e 's/-0?/./' | sed -e 's/-0?/./')
 
 # File exists and has zero size -> not a prerelease
 if [[ -e prerelease.txt && ! -s prerelease.txt ]]; then
     version_string="$version"
+elif [[ -e prerelease.txt ]]; then
+    version_string="${version}-$(cat prerelease.txt)-${commit_hash}"
 else
+    commit_date=$(git show --format=%ci HEAD | head -n 1 | cut - -b1-10 | sed -e 's/-0?/./' | sed -e 's/-0?/./')
     version_string="${version}-nightly-${commit_date}-${commit_hash}"
 fi