+# recurse_deps CMD NAME [BRANCHPATH...]
+# Recursively eval CMD on all dependencies of NAME.
+# CMD can refer to $_name for queried branch name,
+# $_dep for dependency name,
+# $_depchain for space-seperated branch backtrace,
+# and the $_dep_is_tgish boolean.
+# It can modify $_ret to affect the return value
+# of the whole function.
+# If recurse_deps() hits missing dependencies, it will append
+# them to space-separated $missing_deps list and skip them.
+recurse_deps()
+{
+ _cmd="$1"; shift
+ _name="$1"; # no shift
+ _depchain="$*"
+ _depsfile="$(mktemp -t tg-depsfile.XXXXXX)"
+ git cat-file blob "$_name:.topdeps" >"$_depsfile"
+ _ret=0
+ while read _dep; do
+ if ! git rev-parse --verify "$_dep" >/dev/null 2>&1; then
+ # All hope is lost
+ missing_deps="$missing_deps $_dep"
+ continue
+ fi
+
+ _dep_is_tgish=1
+ git rev-parse --verify "refs/top-bases/$_dep" >/dev/null 2>&1 ||
+ _dep_is_tgish=
+
+ # Shoo shoo, keep our environment alone!
+ [ -z "$_dep_is_tgish" ] ||
+ (recurse_deps "$_cmd" "$_dep" "$@") ||
+ _ret=$?
+
+ eval "$_cmd"
+ done <"$_depsfile"
+ missing_deps="${missing_deps# }"
+ rm "$_depsfile"
+ return $_ret
+}
+
+# branch_needs_update
+# This is a helper function for determining whether given branch
+# is up-to-date wrt. its dependencies. It expects input as if it
+# is called as a recurse_deps() helper.
+# In case the branch does need update, it will echo it together
+# with the branch backtrace on the output (see needs_update()
+# description for details) and set $_ret to non-zero.
+branch_needs_update()
+{
+ _dep_base_uptodate=1
+ if [ -n "$_dep_is_tgish" ]; then
+ branch_contains "$_dep" "refs/top-bases/$_dep" || _dep_base_uptodate=
+ fi
+
+ if [ -z "$_dep_base_uptodate" ]; then
+ # _dep needs to be synced with its base
+ echo ": $_dep $_depchain"
+ _ret=1
+ elif [ -n "$_name" ] && ! branch_contains "refs/top-bases/$_name" "$_dep"; then
+ # Some new commits in _dep
+ echo "$_dep $_depchain"
+ _ret=1
+ fi
+}
+
+# needs_update NAME