pager: find out the terminal width before spawning the pager

term_columns() checks for terminal width via ioctl(2) on the standard
output, but we spawn the pager too early for this check to be useful.

The effect of this buglet can be observed by opening a wide terminal and
running "git -p help --all", which still shows 80-column output, while
"git help --all" uses the full terminal width. Run the check before we
spawn the pager to fix this.

While at it, move term_columns() to pager.c and export it from cache.h so
that callers other than the help subsystem can use it.

Signed-off-by: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/pager.c b/pager.c
index 975955b..b790967 100644
--- a/pager.c
+++ b/pager.c
@@ -76,6 +76,12 @@ void setup_pager(void)
 	if (!pager)
 		return;
 
+	/*
+	 * force computing the width of the terminal before we redirect
+	 * the standard output to the pager.
+	 */
+	(void) term_columns();
+
 	setenv("GIT_PAGER_IN_USE", "true", 1);
 
 	/* spawn the pager */
@@ -110,3 +116,34 @@ 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 environment variable (if
+ * set and positive) or ioctl(1, TIOCGWINSZ).ws_col (if positive),
+ * and default to 80 if all else fails.
+ */
+int term_columns(void)
+{
+	static int term_columns_at_startup;
+
+	char *col_string;
+	int n_cols;
+
+	if (term_columns_at_startup)
+		return term_columns_at_startup;
+
+	term_columns_at_startup = 80;
+
+	col_string = getenv("COLUMNS");
+	if (col_string && (n_cols = atoi(col_string)) > 0)
+		term_columns_at_startup = n_cols;
+#ifdef TIOCGWINSZ
+	else {
+		struct winsize ws;
+		if (!ioctl(1, TIOCGWINSZ, &ws) && ws.ws_col)
+			term_columns_at_startup = ws.ws_col;
+	}
+#endif
+
+	return term_columns_at_startup;
+}