tests: use egrep with regular expression branches for compatibility

GNU grep allows you to use "a\|b" in a regular expression to match either
"a" or "b", but at least Solaris grep does not; only egrep allows for that.
And egrep considers "a+" to be "a{1,}" instead of an "a" and a literal plus
sign, so escape that as well.

tests/test-command-template.t

@@ -120,7 +120,7 b' as default style, except for extra phase'
   $ hg log --style default > style.out
   $ cmp log.out style.out || diff -u log.out style.out
   $ hg log -T phases > phases.out
-  $ diff -U 0 log.out phases.out | grep -v '^---\|^+++'
+  $ diff -U 0 log.out phases.out | egrep -v '^---|^\+\+\+'
   @@ -2,0 +3 @@
   +phase:       draft
   @@ -6,0 +8 @@
@@ -146,7 +146,7 b' as default style, except for extra phase'
   $ hg log -v --style default > style.out
   $ cmp log.out style.out || diff -u log.out style.out
   $ hg log -v -T phases > phases.out
-  $ diff -U 0 log.out phases.out | grep -v '^---\|^+++'
+  $ diff -U 0 log.out phases.out | egrep -v '^---|^\+\+\+'
   @@ -2,0 +3 @@
   +phase:       draft
   @@ -7,0 +9 @@
@@ -212,7 +212,7 b' Default style should also preserve color'
   $ hg --color=debug log --style default > style.out
   $ cmp log.out style.out || diff -u log.out style.out
   $ hg --color=debug log -T phases > phases.out
-  $ diff -U 0 log.out phases.out | grep -v '^---\|^+++'
+  $ diff -U 0 log.out phases.out | egrep -v '^---|^\+\+\+'
   @@ -2,0 +3 @@
   +[log.phase|phase:       draft]
   @@ -6,0 +8 @@
@@ -238,7 +238,7 b' Default style should also preserve color'
   $ hg --color=debug -v log --style default > style.out
   $ cmp log.out style.out || diff -u log.out style.out
   $ hg --color=debug -v log -T phases > phases.out
-  $ diff -U 0 log.out phases.out | grep -v '^---\|^+++'
+  $ diff -U 0 log.out phases.out | egrep -v '^---|^\+\+\+'
   @@ -2,0 +3 @@
   +[log.phase|phase:       draft]
   @@ -7,0 +9 @@