tests: eliminate use of sed -i (which fails on NetBSD)

tests/test-diff-change

@@ -1,61 +1,63 b''
 #!/bin/sh -e
 
 # test of hg diff --change
 
 set -e
 
 ec() {
 	echo "invoking $@:"
 	"$@"
 }
 
 hg init a
 cd a
 
 echo "first" > file.txt
 hg add file.txt
 hg commit -m 'first commit' # 0
 
 echo "second" > file.txt
 hg commit -m 'second commit' # 1
 
 echo "third" > file.txt
 hg commit -m 'third commit' # 2
 
 ec hg diff --nodates --change 1
 
 echo
 
 #rev=$(hg log -r 1 --template '{node|short}')
 rev=e9b286083166
 ec hg diff --nodates --change "$rev"
 
 ##
 # Testing diff -c when merge
 
 for i in 1 2 3 4 5 6 7 8 9 10; do
     echo $i >> file.txt
 done
 hg commit -m "lots of text" # 3
 
-sed -i -e 's,^2$,x,' file.txt
+sed -e 's,^2$,x,' file.txt > file.txt.tmp
+mv file.txt.tmp file.txt
 hg commit -m "changed 2 to x" # 4
 
 hg up -r 3 > /dev/null 2>&1 # updated, merged, removed, unresolved
-sed -i -e 's,^8$,y,' file.txt
+sed -e 's,^8$,y,' file.txt > file.txt.tmp
+mv file.txt.tmp file.txt
 hg commit -m "change 8 to y" > /dev/null 2>&1 # 5 # created new head
 
 hg up -C -r 4 > /dev/null 2>&1 # updated, merged, removed, unresolved
 hg merge -r 5 > /dev/null 2>&1 # updated, merged, removed, unresolved
 hg commit -m "merging 8 to y" # 6
 
 echo
 ec hg diff --nodates --change 6 # must be similar to hg diff --nodates --change 5
 
 #echo
 #hg log
 
 echo
 echo "EOF"
 
 # vim: set ts=4 sw=4 et: