cindex: attempt to give oldest commits lowest docids

Monotonically increasing docids may help us avoid sorting output
for the web and CLI, since recent commits are generally the most
desired search results.

`git log --reverse' incurs no extra overhead in this case, since
`--stdin' will mean git buffers the commit list in memory before
attempting to emit anything.

diff --git a/lib/PublicInbox/CodeSearchIdx.pm b/lib/PublicInbox/CodeSearchIdx.pm
index 176422d0d5b2cc69a2ed5b0334256befdf9f6315..f0b506da08cec37456694f27d7c25a43e41fcd24 100644 (file)
--- a/lib/PublicInbox/CodeSearchIdx.pm
+++ b/lib/PublicInbox/CodeSearchIdx.pm
@@ -52,8 +52,12 @@ our $SEEN_MAX = 100000;
 
 # TODO: do we care about committer name + email? or tree OID?
 my @FMT = qw(H P ct an ae at s b); # (b)ody must be last
+
+# git log --stdin buffers all commits before emitting, thus --reverse
+# doesn't incur extra overhead.  We use --reverse to keep Xapian docids
+# increasing so we may be able to avoid sorting results in some cases
 my @LOG_STDIN = (qw(log --no-decorate --no-color --no-notes -p --stat -M
-       --stdin --no-walk=unsorted), '--pretty=format:%n%x00'.
+       --reverse --stdin --no-walk=unsorted), '--pretty=format:%n%x00'.
        join('%n', map { "%$_" } @FMT));
 
 sub new {