pager: set $LESS only when missing

This matches the git behavior. From [1],

> When the `LESS` environment variable is unset, Git sets it to `FRX`
> (if `LESS` environment variable is set, Git does not change it at
> all).

The default $LESS is changed from FRSX to FRX since git 2.1.0 [2]. This
change also updates the default $LESS for repo.

[1] https://git-scm.com/docs/git-config#Documentation/git-config.txt-corepager
[2] https://github.com/git/git/commit/b3275838d969b7ecb91aae584226fccbeb046aca

Bug: https://crbug.com/gerrit/16973
Change-Id: I64ccaa7b034fdb6a92c10025e47f5d07e85e6451
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/374894
Reviewed-by: Chih-Hsuan Yen <x5f4qvj3w3ge2tiq@chyen.cc>
Reviewed-by: Mike Frysinger <vapier@google.com>
Tested-by: Chih-Hsuan Yen <x5f4qvj3w3ge2tiq@chyen.cc>

1 files changed, 4 insertions, 1 deletions

diff --git a/pager.py b/pager.py
index dbd5ae85..2d51b45d 100644
--- a/pager.py
+++ b/pager.py
@@ -118,7 +118,10 @@ def _BecomePager(pager):
     # available versions of 'less', a better 'more'.
     _a, _b, _c = select.select([0], [], [0])
 
-    os.environ["LESS"] = "FRSX"
+    # This matches the behavior of git, which sets $LESS to `FRX` if it is not
+    # set. See:
+    # https://git-scm.com/docs/git-config#Documentation/git-config.txt-corepager
+    os.environ.setdefault("LESS", "FRX")
 
     try:
         os.execvp(pager, [pager])