A pane's child runs with PAGER=cat and GIT_PAGER=cat where the user's environment sets neither, so a pty/run or a command pane never hangs in a pager

git log or man run through pty/run, or in a command pane, sat in less
at its first screen: no one presses q, and the run never answers. The
child's environment now names cat as the pager when the inherited one
names none; a user's own PAGER or GIT_PAGER is kept. It is every pane
child's, a terminal's shell too, since a pty/run's line runs in it.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 28 insertions, 0 deletions

diff --git a/src/host_io.zig b/src/host_io.zig
index ebe910aa..1fab3729 100644
--- a/src/host_io.zig
+++ b/src/host_io.zig
@@ -1268,6 +1268,18 @@ pub const ChildEnv = struct {
             slots[n] = entry;
             n += 1;
         }
+        // No pager to wait in: a pty/run or a command pane's output is read
+        // whole, and less would hold it at its first screen for ever. Only
+        // where the inherited environment chose none.
+        for (defaults) |default| {
+            const set = for (libc.environ[0..i]) |entry| {
+                if (std.mem.eql(u8, name(entry.?), name(default))) break true;
+            } else false;
+            if (set) continue;
+            if (n + own.len + 2 > slots.len) return null;
+            slots[n] = default;
+            n += 1;
+        }
         for (own) |mine| {
             slots[n] = mine;
             n += 1;
@@ -1275,6 +1287,9 @@ pub const ChildEnv = struct {
         slots[n] = null;
         return @ptrCast(slots);
     }
+
+    /// Set for a pane's child only when the user's environment has none.
+    const defaults = [_][*:0]const u8{ "PAGER=cat", "GIT_PAGER=cat" };
 };
 
 test "the child environment replaces the launcher's terminal identity exactly once" {
@@ -1304,6 +1319,10 @@ test "the child environment replaces the launcher's terminal identity exactly on
     var colorterms: usize = 0;
     var probes: usize = 0;
     var dumb = false;
+    var pagers: usize = 0;
+    var git_pagers: usize = 0;
+    var pager_cat = false;
+    var git_pager_cat = false;
     var i: usize = 0;
     while (envp[i]) |entry| : (i += 1) {
         const line = std.mem.span(entry);
@@ -1311,7 +1330,16 @@ test "the child environment replaces the launcher's terminal identity exactly on
         if (std.mem.startsWith(u8, line, "COLORTERM=")) colorterms += 1;
         if (std.mem.eql(u8, line, "TERM=dumb")) dumb = true;
         if (std.mem.eql(u8, line, "PARDES_CHILD_ENV_PROBE=1")) probes += 1;
+        if (std.mem.startsWith(u8, line, "PAGER=")) pagers += 1;
+        if (std.mem.startsWith(u8, line, "GIT_PAGER=")) git_pagers += 1;
+        if (std.mem.eql(u8, line, "PAGER=cat")) pager_cat = true;
+        if (std.mem.eql(u8, line, "GIT_PAGER=cat")) git_pager_cat = true;
     }
+    // A pager only where the user named none: cat, so nothing waits in less.
+    try std.testing.expectEqual(@as(usize, 1), pagers);
+    try std.testing.expectEqual(@as(usize, 1), git_pagers);
+    if (std.c.getenv("PAGER") == null) try std.testing.expect(pager_cat);
+    if (std.c.getenv("GIT_PAGER") == null) try std.testing.expect(git_pager_cat);
     try std.testing.expectEqual(@as(usize, 1), terms);
     try std.testing.expectEqual(@as(usize, 1), colorterms);
     try std.testing.expectEqual(@as(usize, 1), probes);