Re: [TopGit PATCH] hooks/pre-commit: check for cycles in dependencies

Only newly added dependencies needs to be considered.  For each of these deps
check if there is a path from this dep to the current HEAD.

Use recursive_dep() for this task.  Even if recursive_dep() uses a DFS-like
traversal it will not run into an infty-loop if there would be a cycle, because
recursive_dep() takes .topdeps only from committed trees.  And it is required
that the committed dependency graph is acyclic.

Signed-off-by: Bert Wesarg <redacted>

---
 hooks/pre-commit.sh |   30 ++++++++++++++++++++++++++++--
 1 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/hooks/pre-commit.sh b/hooks/pre-commit.sh
index 9d677e9..8e05a4e 100644
--- a/hooks/pre-commit.sh
+++ b/hooks/pre-commit.sh

@@ -20,7 +20,8 @@ tg_util

 if head_=$(git symbolic-ref -q HEAD); then
       case "$head_" in
               refs/heads/*)
-                       git rev-parse -q --verify "refs/top-bases${head_#refs/heads}" >/dev/null || exit 0;;
+                       head_="${head_#refs/heads/}"
+                       git rev-parse -q --verify "refs/top-bases/$head_" >/dev/null || exit 0;;
               *)
                       exit 0;;
       esac

@@ -35,4 +36,29 @@ fi

 [ -s "$root_dir/.topmsg" ] ||
       die ".topmsg is missing"

-# TODO: Verify .topdeps for valid branch names and against cycles
+check_cycle_name()
+{
+       [ "$head_" != "$_dep" ] ||
+               die "TopGit dependencies form a cycle: perpetrator is $_name"
+}
+
+# only check newly added deps
+# check if a path exists to the current HEAD
+git diff --cached "$root_dir/.topdeps" |
+       awk '
+BEGIN      { in_hunk = 0; }
+/^@@ /     { in_hunk = 1; }
+/^\+/      { if (in_hunk == 1) printf("%s\n", substr($0, 2)); }
+/^[^@ +-]/ { in_hunk = 0; }
+' |
+       while read newly_added; do
+               # deps can be non-tgish but we can't run recurse_deps() on them
+               ref_exists "refs/top-bases/$newly_added" ||
+                       continue