tests: avoid non-portable sed command
sed -i is a GNU extension and the i command without newline as well.
Just create the file from scratch with printf to side-step the issue.
--- a/tests/test-evolve-public-content-divergent-main.t Thu Apr 09 19:51:03 2020 +0200
+++ b/tests/test-evolve-public-content-divergent-main.t Thu Apr 09 19:52:30 2020 +0200
@@ -43,7 +43,7 @@
Make an amend and change phase to public:
- $ sed -i "1 i I am first" b
+ $ printf "I am first\nb\n" > b
$ hg amend
$ hg phase --public