Merge branch 'jn/maint-fix-pager' into maint

* jn/maint-fix-pager:
  tests: Fix race condition in t7006-pager
  t7006-pager: if stdout is not a terminal, make a new one
  tests: Add tests for automatic use of pager
  am: Fix launching of pager
  git svn: Fix launching of pager
  git.1: Clarify the behavior of the --paginate option
  Make 'git var GIT_PAGER' always print the configured pager
  Fix 'git var' usage synopsis

Documentation/git-var.txt

@@ -8,7 +8,7 @@ git-var - Show a git logical variable
 
 SYNOPSIS
 --------
-'git var' [ -l | <variable> ]
+'git var' ( -l | <variable> )
 
 DESCRIPTION
 -----------

Documentation/git.txt

@@ -230,7 +230,10 @@ help ...`.
 
 -p::
 --paginate::
-	Pipe all output into 'less' (or if set, $PAGER).
+	Pipe all output into 'less' (or if set, $PAGER) if standard
+	output is a terminal.  This overrides the `pager.<cmd>`
+	configuration options (see the "Configuration Mechanism" section
+	below).
 
 --no-pager::
 	Do not pipe git output into a pager.
@@ -402,7 +405,8 @@ people.  Here is an example:
 ------------
 
 Various commands read from the configuration file and adjust
-their operation accordingly.
+their operation accordingly.  See linkgit:git-config[1] for a
+list.
 
 
 Identifier Terminology

builtin-var.c

@@ -6,7 +6,7 @@
 #include "cache.h"
 #include "exec_cmd.h"
 
-static const char var_usage[] = "git var [-l | <variable>]";
+static const char var_usage[] = "git var (-l | <variable>)";
 
 static const char *editor(int flag)
 {
@@ -20,7 +20,7 @@ static const char *editor(int flag)
 
 static const char *pager(int flag)
 {
-	const char *pgm = git_pager();
+	const char *pgm = git_pager(1);
 
 	if (!pgm)
 		pgm = "cat";

cache.h

@@ -775,7 +775,7 @@ extern const char *git_committer_info(int);
 extern const char *fmt_ident(const char *name, const char *email, const char *date_str, int);
 extern const char *fmt_name(const char *name, const char *email);
 extern const char *git_editor(void);
-extern const char *git_pager(void);
+extern const char *git_pager(int stdout_is_tty);
 
 struct checkout {
 	const char *base_dir;

git-am.sh

@@ -663,10 +663,7 @@ do
 		[eE]*) git_editor "$dotest/final-commit"
 		       action=again ;;
 		[vV]*) action=again
-		       : ${GIT_PAGER=$(git var GIT_PAGER)}
-		       : ${LESS=-FRSX}
-		       export LESS
-		       $GIT_PAGER "$dotest/patch" ;;
+		       git_pager "$dotest/patch" ;;
 		*)     action=again ;;
 		esac
 	    done

git-sh-setup.sh

@@ -107,6 +107,19 @@ git_editor() {
 	eval "$GIT_EDITOR" '"$@"'
 }
 
+git_pager() {
+	if test -t 1
+	then
+		GIT_PAGER=$(git var GIT_PAGER)
+	else
+		GIT_PAGER=cat
+	fi
+	: ${LESS=-FRSX}
+	export LESS
+
+	eval "$GIT_PAGER" '"$@"'
+}
+
 sane_grep () {
 	GREP_OPTIONS= LC_ALL=C grep "$@"
 }

git-svn.perl

@@ -5459,7 +5459,12 @@ sub git_svn_log_cmd {
 
 # adapted from pager.c
 sub config_pager {
-	chomp(my $pager = command_oneline(qw(var GIT_PAGER)));
+	if (! -t *STDOUT) {
+		$ENV{GIT_PAGER_IN_USE} = 'false';
+		$pager = undef;
+		return;
+	}
+	chomp($pager = command_oneline(qw(var GIT_PAGER)));
 	if ($pager eq 'cat') {
 		$pager = undef;
 	}
@@ -5467,7 +5472,7 @@ sub config_pager {
 }
 
 sub run_pager {
-	return unless -t *STDOUT && defined $pager;
+	return unless defined $pager;
 	pipe my ($rfd, $wfd) or return;
 	defined(my $pid = fork) or ::fatal "Can't fork: $!";
 	if (!$pid) {

pager.c

@@ -48,11 +48,11 @@ static void wait_for_pager_signal(int signo)
 	raise(signo);
 }
 
-const char *git_pager(void)
+const char *git_pager(int stdout_is_tty)
 {
 	const char *pager;
 
-	if (!isatty(1))
+	if (!stdout_is_tty)
 		return NULL;
 
 	pager = getenv("GIT_PAGER");
@@ -73,7 +73,7 @@ const char *git_pager(void)
 
 void setup_pager(void)
 {
-	const char *pager = git_pager();
+	const char *pager = git_pager(isatty(1));
 
 	if (!pager)
 		return;

t/t7006-pager.sh

@@ -0,0 +1,176 @@
+#!/bin/sh
+
+test_description='Test automatic use of a pager.'
+
+. ./test-lib.sh
+
+rm -f stdout_is_tty
+test_expect_success 'set up terminal for tests' '
+	if test -t 1
+	then
+		: > stdout_is_tty
+	elif
+		test_have_prereq PERL &&
+		"$PERL_PATH" "$TEST_DIRECTORY"/t7006/test-terminal.perl \
+			sh -c "test -t 1"
+	then
+		: > test_terminal_works
+	fi
+'
+
+if test -e stdout_is_tty
+then
+	test_terminal() { "$@"; }
+	test_set_prereq TTY
+elif test -e test_terminal_works
+then
+	test_terminal() {
+		"$PERL_PATH" "$TEST_DIRECTORY"/t7006/test-terminal.perl "$@"
+	}
+	test_set_prereq TTY
+else
+	say no usable terminal, so skipping some tests
+fi
+
+unset GIT_PAGER GIT_PAGER_IN_USE
+git config --unset core.pager
+PAGER='cat > paginated.out'
+export PAGER
+
+test_expect_success 'setup' '
+	test_commit initial
+'
+
+rm -f paginated.out
+test_expect_success TTY 'some commands use a pager' '
+	test_terminal git log &&
+	test -e paginated.out
+'
+
+rm -f paginated.out
+test_expect_success TTY 'some commands do not use a pager' '
+	test_terminal git rev-list HEAD &&
+	! test -e paginated.out
+'
+
+rm -f paginated.out
+test_expect_success 'no pager when stdout is a pipe' '
+	git log | cat &&
+	! test -e paginated.out
+'
+
+rm -f paginated.out
+test_expect_success 'no pager when stdout is a regular file' '
+	git log > file &&
+	! test -e paginated.out
+'
+
+rm -f paginated.out
+test_expect_success TTY 'git --paginate rev-list uses a pager' '
+	test_terminal git --paginate rev-list HEAD &&
+	test -e paginated.out
+'
+
+rm -f file paginated.out
+test_expect_success 'no pager even with --paginate when stdout is a pipe' '
+	git --paginate log | cat &&
+	! test -e paginated.out
+'
+
+rm -f paginated.out
+test_expect_success TTY 'no pager with --no-pager' '
+	test_terminal git --no-pager log &&
+	! test -e paginated.out
+'
+
+# A colored commit log will begin with an appropriate ANSI escape
+# for the first color; the text "commit" comes later.
+colorful() {
+	read firstline < $1
+	! expr "$firstline" : "^[a-zA-Z]" >/dev/null
+}
+
+rm -f colorful.log colorless.log
+test_expect_success 'tests can detect color' '
+	git log --no-color > colorless.log &&
+	git log --color > colorful.log &&
+	! colorful colorless.log &&
+	colorful colorful.log
+'
+
+rm -f colorless.log
+git config color.ui auto
+test_expect_success 'no color when stdout is a regular file' '
+	git log > colorless.log &&
+	! colorful colorless.log
+'
+
+rm -f paginated.out
+git config color.ui auto
+test_expect_success TTY 'color when writing to a pager' '
+	TERM=vt100 test_terminal git log &&
+	colorful paginated.out
+'
+
+rm -f colorful.log
+git config color.ui auto
+test_expect_success 'color when writing to a file intended for a pager' '
+	TERM=vt100 GIT_PAGER_IN_USE=true git log > colorful.log &&
+	colorful colorful.log
+'
+
+unset PAGER GIT_PAGER
+git config --unset core.pager
+test_expect_success 'determine default pager' '
+	less=$(git var GIT_PAGER) &&
+	test -n "$less"
+'
+
+if expr "$less" : '^[a-z]*$' > /dev/null && test_have_prereq TTY
+then
+	test_set_prereq SIMPLEPAGER
+fi
+
+unset PAGER GIT_PAGER
+git config --unset core.pager
+rm -f default_pager_used
+test_expect_success SIMPLEPAGER 'default pager is used by default' '
+	cat > $less <<-EOF &&
+	#!$SHELL_PATH
+	wc > default_pager_used
+	EOF
+	chmod +x $less &&
+	PATH=.:$PATH test_terminal git log &&
+	test -e default_pager_used
+'
+
+unset GIT_PAGER
+git config --unset core.pager
+rm -f PAGER_used
+test_expect_success TTY 'PAGER overrides default pager' '
+	PAGER="wc > PAGER_used" &&
+	export PAGER &&
+	test_terminal git log &&
+	test -e PAGER_used
+'
+
+unset GIT_PAGER
+rm -f core.pager_used
+test_expect_success TTY 'core.pager overrides PAGER' '
+	PAGER=wc &&
+	export PAGER &&
+	git config core.pager "wc > core.pager_used" &&
+	test_terminal git log &&
+	test -e core.pager_used
+'
+
+rm -f GIT_PAGER_used
+test_expect_success TTY 'GIT_PAGER overrides core.pager' '
+	git config core.pager wc &&
+	GIT_PAGER="wc > GIT_PAGER_used" &&
+	export GIT_PAGER &&
+	test_terminal git log &&
+	test -e GIT_PAGER_used
+'
+
+test_done

t/t7006/test-terminal.perl

@@ -0,0 +1,58 @@
+#!/usr/bin/perl
+use strict;
+use warnings;
+use IO::Pty;
+use File::Copy;
+
+# Run @$argv in the background with stdout redirected to $out.
+sub start_child {
+	my ($argv, $out) = @_;
+	my $pid = fork;
+	if (not defined $pid) {
+		die "fork failed: $!"
+	} elsif ($pid == 0) {
+		open STDOUT, ">&", $out;
+		close $out;
+		exec(@$argv) or die "cannot exec '$argv->[0]': $!"
+	}
+	return $pid;
+}
+
+# Wait for $pid to finish.
+sub finish_child {
+	# Simplified from wait_or_whine() in run-command.c.
+	my ($pid) = @_;
+
+	my $waiting = waitpid($pid, 0);
+	if ($waiting < 0) {
+		die "waitpid failed: $!";
+	} elsif ($? & 127) {
+		my $code = $? & 127;
+		warn "died of signal $code";
+		return $code - 128;
+	} else {
+		return $? >> 8;
+	}
+}
+
+sub xsendfile {
+	my ($out, $in) = @_;
+
+	# Note: the real sendfile() cannot read from a terminal.
+
+	# It is unspecified by POSIX whether reads
+	# from a disconnected terminal will return
+	# EIO (as in AIX 4.x, IRIX, and Linux) or
+	# end-of-file.  Either is fine.
+	copy($in, $out, 4096) or $!{EIO} or die "cannot copy from child: $!";
+}
+
+if ($#ARGV < 1) {
+	die "usage: test-terminal program args";
+}
+my $master = new IO::Pty;
+my $slave = $master->slave;
+my $pid = start_child(\@ARGV, $slave);
+close $slave;
+xsendfile(\*STDOUT, $master);
+exit(finish_child($pid));