Make a post-merge hook that logs a message when the git hooks are updated in master

We have some great git hooks, but they are going to get out of date.

We don't want to manually copy updates to our repositories: that's a security risk.

But it would be great if we had a post-merge (post pull) hook that logged an obvious message when the hooks in .git are different from the hooks in master's scripts/maint.

For bonus points: log a diff between the .git hooks and the scripts/maint hooks.

changed milestone to %Tor: 0.4.1.x-final

added 041-proposed asn-merge component::core tor/tor git-scripts milestone::Tor: 0.4.1.x-final owner::rl1987 points::1 priority::medium resolution::fixed reviewer::nickm severity::normal status::closed type::enhancement labels

For extra bonus points, also log a message when the merge scripts in #29391 (moved) are updated. I guess we can find them using command -v?

Trac:
Cc: N/A to rl1987

Trac:
Owner: N/A to rl1987
Status: new to accepted

https://github.com/torproject/tor/pull/750

Trac:
Status: accepted to needs_review

Trac:
Reviewer: N/A to nickm

Hi! This is a good start. I've asked a few questions on the PR.

Trac:
Status: needs_review to needs_revision

Trac:
Status: needs_revision to needs_review

I've added a question and noted another issue. The issue makes me worry that maybe this script hasn't been tested: please test it to make sure it works before putting it into needs_review again?

Trac:
Status: needs_review to needs_revision

Hello, sorry about that. I fixed the issues and opened a new pull request to clean up a git history and resolve a merge conflict: https://github.com/torproject/tor/pull/780

It works now:

vagrant@stretch:~/tor$ cp scripts/git/post-merge.git-hook .git/hooks/post-merge 
vagrant@stretch:~/tor$ git rev-parse --abbrev-ref HEAD
ticket29588_2
vagrant@stretch:~/tor$ echo "###" >> .git/hooks/post-merge 
vagrant@stretch:~/tor$ git reset --hard HEAD~2
HEAD is now at 5f253f6a4 Iterate over contents of scripts/git with check_for_script_update function
vagrant@stretch:~/tor$ git pull
Updating 5f253f6a4..0befdb8a3
Fast-forward
 scripts/git/post-merge.git-hook | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
ATTENTION: post-merge hook has changed:
===============================
--- /home/vagrant/tor/.git/hooks/post-merge	2019-03-10 16:45:14.000000000 +0000
+++ /home/vagrant/tor/scripts/git/post-merge.git-hook	2019-03-10 16:45:36.000000000 +0000
@@ -43,4 +43,3 @@
         check_for_script_update "$file"
 done
 
-###
ATTENTION: /home/vagrant/tor/scripts/git/post-merge.git-hook has changed:
diff --git a/scripts/git/post-merge.git-hook b/scripts/git/post-merge.git-hook
index ed0e16279..176b7c9bb 100755
--- a/scripts/git/post-merge.git-hook
+++ b/scripts/git/post-merge.git-hook
@@ -20,7 +20,7 @@ check_for_diffs() {
                then
                         echo "ATTENTION: $1 hook has changed:"
                         echo "==============================="
-                        diff "$installed" "$latest"
+                        diff -u "$installed" "$latest"
                fi
         fi
 }
@@ -31,7 +31,7 @@ check_for_script_update() {
         if ! git diff ORIG_HEAD HEAD --exit-code -- "$fullpath" >/dev/null
         then
                 echo "ATTENTION: $1 has changed:"
-                git diff ORIG_HEAD HEAD -- "$fullpath"
+                git --no-pager diff ORIG_HEAD HEAD -- "$fullpath"
         fi
 }

Trac:
Status: needs_revision to needs_review

LGTM now. Thanks!

Trac:
Status: needs_review to merge_ready
Keywords: N/A deleted, asn-merge added
Milestone: Tor: unspecified to Tor: 0.4.1.x-final

Merged!

Trac:
Status: merge_ready to closed
Resolution: N/A to fixed

closed

changed time estimate to 8h

mentioned in issue #31040 (moved)

moved to tpo/core/tor#29588 (closed)

mentioned in issue tpo/core/tor#31040 (closed)