pager: move pager-specific setup into the build

Allowing PAGER_ENV to be set at build-time allows us to move
pager-specific knowledge out of our build.  This allows us to
set a better default for FreeBSD more(1), which pretends not to
understand ANSI color escapes if the MORE environment variable
is left empty, but accepts the same variables as less(1)

Originally-from:
 https://public-inbox.org/git/xmqq61piw4yf.fsf@gitster.dls.corp.google.com/

Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Eric Wong <e@80x24.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -367,6 +367,14 @@ all::
 # Define HAVE_BSD_SYSCTL if your platform has a BSD-compatible sysctl function.
 #
 # Define HAVE_GETDELIM if your system has the getdelim() function.
+#
+# Define PAGER_ENV to a SP separated VAR=VAL pairs to define
+# default environment variables to be passed when a pager is spawned, e.g.
+#
+#    PAGER_ENV = LESS=FRX LV=-c
+#
+# to say "export LESS=FRX (and LV=-c) if the environment variable
+# LESS (and LV) is not set, respectively".
 
 GIT-VERSION-FILE: FORCE
 	@$(SHELL_PATH) ./GIT-VERSION-GEN
@@ -1492,6 +1500,10 @@ ifeq ($(PYTHON_PATH),)
 NO_PYTHON = NoThanks
 endif
 
+ifndef PAGER_ENV
+PAGER_ENV = LESS=FRX LV=-c
+endif
+
 QUIET_SUBDIR0  = +$(MAKE) -C # space to separate -C and subdir
 QUIET_SUBDIR1  =
 
@@ -1613,6 +1625,11 @@ ifdef DEFAULT_HELP_FORMAT
 BASIC_CFLAGS += -DDEFAULT_HELP_FORMAT='"$(DEFAULT_HELP_FORMAT)"'
 endif
 
+PAGER_ENV_SQ = $(subst ','\'',$(PAGER_ENV))
+PAGER_ENV_CQ = "$(subst ",\",$(subst \,\\,$(PAGER_ENV)))"
+PAGER_ENV_CQ_SQ = $(subst ','\'',$(PAGER_ENV_CQ))
+BASIC_CFLAGS += -DPAGER_ENV='$(PAGER_ENV_CQ_SQ)'
+
 ALL_CFLAGS += $(BASIC_CFLAGS)
 ALL_LDFLAGS += $(BASIC_LDFLAGS)
 
@@ -1737,7 +1754,7 @@ common-cmds.h: $(wildcard Documentation/git-*.txt)
 
 SCRIPT_DEFINES = $(SHELL_PATH_SQ):$(DIFF_SQ):$(GIT_VERSION):\
 	$(localedir_SQ):$(NO_CURL):$(USE_GETTEXT_SCHEME):$(SANE_TOOL_PATH_SQ):\
-	$(gitwebdir_SQ):$(PERL_PATH_SQ):$(SANE_TEXT_GREP)
+	$(gitwebdir_SQ):$(PERL_PATH_SQ):$(SANE_TEXT_GREP):$(PAGER_ENV)
 define cmd_munge_script
 $(RM) $@ $@+ && \
 sed -e '1s|#!.*/sh|#!$(SHELL_PATH_SQ)|' \
@@ -1750,6 +1767,7 @@ sed -e '1s|#!.*/sh|#!$(SHELL_PATH_SQ)|' \
     -e 's|@@GITWEBDIR@@|$(gitwebdir_SQ)|g' \
     -e 's|@@PERL@@|$(PERL_PATH_SQ)|g' \
     -e 's|@@SANE_TEXT_GREP@@|$(SANE_TEXT_GREP)|g' \
+    -e 's|@@PAGER_ENV@@|$(PAGER_ENV_SQ)|g' \
     $@.sh >$@+
 endef
 
@@ -2153,6 +2171,7 @@ GIT-BUILD-OPTIONS: FORCE
 	@echo NO_PERL=\''$(subst ','\'',$(subst ','\'',$(NO_PERL)))'\' >>$@+
 	@echo NO_PYTHON=\''$(subst ','\'',$(subst ','\'',$(NO_PYTHON)))'\' >>$@+
 	@echo NO_UNIX_SOCKETS=\''$(subst ','\'',$(subst ','\'',$(NO_UNIX_SOCKETS)))'\' >>$@+
+	@echo PAGER_ENV=\''$(subst ','\'',$(subst ','\'',$(PAGER_ENV)))'\' >>$@+
 ifdef TEST_OUTPUT_DIRECTORY
 	@echo TEST_OUTPUT_DIRECTORY=\''$(subst ','\'',$(subst ','\'',$(TEST_OUTPUT_DIRECTORY)))'\' >>$@+
 endif

config.mak.uname

@@ -206,6 +206,7 @@ ifeq ($(uname_S),FreeBSD)
 	HAVE_PATHS_H = YesPlease
 	GMTIME_UNRELIABLE_ERRORS = UnfortunatelyYes
 	HAVE_BSD_SYSCTL = YesPlease
+	PAGER_ENV = LESS=FRX LV=-c MORE=FRX
 endif
 ifeq ($(uname_S),OpenBSD)
 	NO_STRCASESTR = YesPlease

git-sh-setup.sh

@@ -160,9 +160,11 @@ git_pager() {
 	else
 		GIT_PAGER=cat
 	fi
-	: "${LESS=-FRX}"
-	: "${LV=-c}"
-	export LESS LV
+	for vardef in @@PAGER_ENV@@
+	do
+		var=${vardef%%=*}
+		eval ": \"\${$vardef}\" && export $var"
+	done
 
 	eval "$GIT_PAGER" '"$@"'
 }

pager.c

@@ -63,14 +63,38 @@ const char *git_pager(int stdout_is_tty)
 	return pager;
 }
 
+static void setup_pager_env(struct argv_array *env)
+{
+	const char **argv;
+	int i;
+	char *pager_env = xstrdup(PAGER_ENV);
+	int n = split_cmdline(pager_env, &argv);
+
+	if (n < 0)
+		die("malformed build-time PAGER_ENV: %s",
+			split_cmdline_strerror(n));
+
+	for (i = 0; i < n; i++) {
+		char *cp = strchr(argv[i], '=');
+
+		if (!cp)
+			die("malformed build-time PAGER_ENV");
+
+		*cp = '\0';
+		if (!getenv(argv[i])) {
+			*cp = '=';
+			argv_array_push(env, argv[i]);
+		}
+	}
+	free(pager_env);
+	free(argv);
+}
+
 void prepare_pager_args(struct child_process *pager_process, const char *pager)
 {
 	argv_array_push(&pager_process->args, pager);
 	pager_process->use_shell = 1;
-	if (!getenv("LESS"))
-		argv_array_push(&pager_process->env_array, "LESS=FRX");
-	if (!getenv("LV"))
-		argv_array_push(&pager_process->env_array, "LV=-c");
+	setup_pager_env(&pager_process->env_array);
 }
 
 void setup_pager(void)

t/t7006-pager.sh

@@ -49,6 +49,19 @@ test_expect_success TTY 'LESS and LV envvars are set for pagination' '
 	grep ^LV= pager-env.out
 '
 
+test_expect_success !MINGW,TTY 'LESS and LV envvars set by git-sh-setup' '
+	(
+		sane_unset LESS LV &&
+		PAGER="env >pager-env.out; wc" &&
+		export PAGER &&
+		PATH="$(git --exec-path):$PATH" &&
+		export PATH &&
+		test_terminal sh -c ". git-sh-setup && git_pager"
+	) &&
+	grep ^LESS= pager-env.out &&
+	grep ^LV= pager-env.out
+'
+
 test_expect_success TTY 'some commands do not use a pager' '
 	rm -f paginated.out &&
 	test_terminal git rev-list HEAD &&