[PATCH 1/2] Save terminal width before setting up pager and export term_columns()

["Zbigniew Jędrzejewski-Szmek" <zbyszek@in.waw.pl>]

term_columns() checks for terminal width via ioctl(2). After
redirecting, stdin is no longer terminal to get terminal width.

Check terminal width and save it before redirecting stdin in
setup_pager() by calling term_columns().

Move term_columns() to pager.c and export it in cache.h.

Signed-off-by: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
---
 cache.h |  1 +
 help.c  | 22 -------------------
 pager.c | 45 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 46 insertions(+), 22 deletions(-)

This replaces cb0850f (Save terminal width before setting up pager -
2012-02-04) from Nguyễn Thái Ngọc Duy and my previous patch to export
term_columns().

This is directly on top of v1.7.9 as requested.

I removed Signed-off-by from Nguyễn and Junio because the patch is
substantially changed.

diff --git a/cache.h b/cache.h
index 10afd71..2f30b3a 100644
--- a/cache.h
+++ b/cache.h
@@ -1175,6 +1175,7 @@ extern void setup_pager(void);
 extern const char *pager_program;
 extern int pager_in_use(void);
 extern int pager_use_color;
+extern int term_columns(void);
 
 extern const char *editor_program;
 extern const char *askpass_program;
diff --git a/help.c b/help.c
index cbbe966..14eefc9 100644
--- a/help.c
+++ b/help.c
@@ -5,28 +5,6 @@
 #include "help.h"
 #include "common-cmds.h"
 
-/* most GUI terminals set COLUMNS (although some don't export it) */
-static int term_columns(void)
-{
-	char *col_string = getenv("COLUMNS");
-	int n_cols;
-
-	if (col_string && (n_cols = atoi(col_string)) > 0)
-		return n_cols;
-
-#ifdef TIOCGWINSZ
-	{
-		struct winsize ws;
-		if (!ioctl(1, TIOCGWINSZ, &ws)) {
-			if (ws.ws_col)
-				return ws.ws_col;
-		}
-	}
-#endif
-
-	return 80;
-}
-
 void add_cmdname(struct cmdnames *cmds, const char *name, int len)
 {
 	struct cmdname *ent = xmalloc(sizeof(*ent) + len + 1);
diff --git a/pager.c b/pager.c
index 975955b..b8049a4 100644
--- a/pager.c
+++ b/pager.c
@@ -76,6 +76,10 @@ void setup_pager(void)
 	if (!pager)
 		return;
 
+	/* prime the term_columns() cache before it is too
+	 * late and stdout is replaced */
+	(void) term_columns();
+
 	setenv("GIT_PAGER_IN_USE", "true", 1);
 
 	/* spawn the pager */
@@ -110,3 +114,44 @@ int pager_in_use(void)
 	env = getenv("GIT_PAGER_IN_USE");
 	return env ? git_config_bool("GIT_PAGER_IN_USE", env) : 0;
 }
+
+/*
+ * Return cached value (if set) or $COLUMNS (if set and positive) or
+ * ioctl(1, TIOCGWINSZ).ws_col (if positive) or 80.
+ *
+ * $COLUMNS even if set, is usually not exported, so
+ * the variable can be used to override autodection.
+ * This behaviour conforms to The Single UNIX Specification, Version 2
+ * (http://pubs.opengroup.org/onlinepubs/7908799/xbd/envvar.html#tag_002_003).
+ */
+int term_columns(void)
+{
+	static int term_columns_cache;
+
+	char *col_string;
+	int n_cols;
+
+	if (term_columns_cache)
+		return term_columns_cache;
+
+	col_string = getenv("COLUMNS");
+	if (col_string && (n_cols = atoi(col_string)) > 0) {
+		term_columns_cache = n_cols;
+		return term_columns_cache;
+	}
+
+#ifdef TIOCGWINSZ
+	{
+		struct winsize ws;
+		if (!ioctl(1, TIOCGWINSZ, &ws)) {
+			if (ws.ws_col) {
+				term_columns_cache = ws.ws_col;
+				return term_columns_cache;
+			}
+		}
+	}
+#endif
+
+	term_columns_cache = 80;
+	return term_columns_cache;
+}
-- 
1.7.9.3.g2429d.dirty