t3508: add check_head_differs_from() helper function and use it

diff --git a/git-am.sh b/git-am.sh
index ef2d51a2b80d77dc5fe28d76b5047a97dc4c0fae..e7f008c7baae2ff484e16882e199b6b9d75195aa 100755 (executable)
--- a/git-am.sh
+++ b/git-am.sh
@@ -596,7 +596,7 @@ do
                        echo "To restore the original branch and stop patching run \"$cmdline --abort\"."
                        stop_here $this
                }
-               rm -f "$dotest/original-commit"
+               rm -f "$dotest/original-commit" "$dotest/author-script"
                if test -f "$dotest/rebasing" &&
                        commit=$(sed -e 's/^From \([0-9a-f]*\) .*/\1/' \
                                -e q "$dotest/$msgnum") &&
@@ -605,6 +605,7 @@ do
                        git cat-file commit "$commit" |
                        sed -e '1,/^$/d' >"$dotest/msg-clean"
                        echo "$commit" > "$dotest/original-commit"
+                       get_author_ident_from_commit "$commit" > "$dotest/author-script"
                else
                        {
                                sed -n '/^Subject/ s/Subject: //p' "$dotest/info"
@@ -616,9 +617,14 @@ do
                ;;
        esac
 
-       GIT_AUTHOR_NAME="$(sed -n '/^Author/ s/Author: //p' "$dotest/info")"
-       GIT_AUTHOR_EMAIL="$(sed -n '/^Email/ s/Email: //p' "$dotest/info")"
-       GIT_AUTHOR_DATE="$(sed -n '/^Date/ s/Date: //p' "$dotest/info")"
+       if test -f "$dotest/author-script"
+       then
+               eval $(cat "$dotest/author-script")
+       else
+               GIT_AUTHOR_NAME="$(sed -n '/^Author/ s/Author: //p' "$dotest/info")"
+               GIT_AUTHOR_EMAIL="$(sed -n '/^Email/ s/Email: //p' "$dotest/info")"
+               GIT_AUTHOR_DATE="$(sed -n '/^Date/ s/Date: //p' "$dotest/info")"
+       fi
 
        if test -z "$GIT_AUTHOR_EMAIL"
        then