From 8c78ddfd5c014069c39e811e825419c8fc3cb299 Mon Sep 17 00:00:00 2001
From: Filippos Giannakos <philipgian@grnet.gr>
Date: Tue, 14 Feb 2017 15:47:03 +0200
Subject: [PATCH] Improve pre-push fileset for a new remote branch

When pushing a branch that does not exist on the remote repository,
instead of blindly running the checks on every file, this commit locates
the first ancestor not present on the remote repository and uses its
parent as the source of the fileset calculation. If it has no parents,
then the remote repository has no common commits and the checks should
be run on all files.
---
 pre_commit/resources/pre-push-tmpl | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/pre_commit/resources/pre-push-tmpl b/pre_commit/resources/pre-push-tmpl
index 4e6ed2bd..81d0dcbe 100644
--- a/pre_commit/resources/pre-push-tmpl
+++ b/pre_commit/resources/pre-push-tmpl
@@ -2,9 +2,19 @@ z40=0000000000000000000000000000000000000000
 while read local_ref local_sha remote_ref remote_sha
 do
     if [ "$local_sha" != $z40 ]; then
-        if [ "$remote_sha" = $z40 ];
-        then
-            args="run --all-files"
+        if [ "$remote_sha" = $z40 ]; then
+            # First ancestor not found in remote
+            first_ancestor=$(git rev-list --topo-order --reverse "$local_sha" --not --remotes="$1" | head -n 1)
+            if [ -n "$first_ancestor" ]; then
+                # Check that the ancestor has at least one parent
+                git rev-list --max-parents=0 "$local_sha" | grep "$first_ancestor" > /dev/null
+                if [ $? -ne 0 ]; then
+                    args="run --all-files"
+                else
+                    source=$(git rev-parse "$first_ancestor"^)
+                    args="run --origin $local_sha --source $source"
+                fi
+            fi
         else
             args="run --origin $local_sha --source $remote_sha"
         fi