[PATCH] help: colorize man pages

[Felipe Contreras <felipe.contreras@gmail.com>]

Our man pages don't contain many useful colors (just blue links),
moreover, many people have groff SGR disabled, so they don't see any
colors with man pages.

We can set LESS_TERMCAP variables to render bold and underlined text
with colors in the pager; a common trick[1].

Bold is rendered as red, underlined as blue, and standout (messages and
highlighted search) as inverse magenta.

This only works when the pager is less, and the color.pager
configuration is enabled, as well as color.ui.

[1] https://unix.stackexchange.com/questions/119/colors-in-man-pages/147

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
---
 builtin/help.c | 27 ++++++++++++++++++++++++++-
 color.h        |  1 +
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/builtin/help.c b/builtin/help.c
index bb339f0fc8..0119e833a8 100644
--- a/builtin/help.c
+++ b/builtin/help.c
@@ -11,6 +11,7 @@
 #include "config-list.h"
 #include "help.h"
 #include "alias.h"
+#include "color.h"
 
 #ifndef DEFAULT_HELP_FORMAT
 #define DEFAULT_HELP_FORMAT "man"
@@ -253,10 +254,33 @@ static void exec_man_konqueror(const char *path, const char *page)
 	}
 }
 
+static void colorize_man(void)
+{
+	if (!pager_use_color || !want_color(GIT_COLOR_UNKNOWN))
+		return;
+
+	/* Disable groff colors */
+	setenv("GROFF_NO_SGR", "1", 0);
+
+	/* Bold */
+	setenv("LESS_TERMCAP_md", GIT_COLOR_BOLD_RED, 0);
+	setenv("LESS_TERMCAP_me", GIT_COLOR_RESET, 0);
+
+	/* Underline */
+	setenv("LESS_TERMCAP_us", GIT_COLOR_BLUE GIT_COLOR_UNDERLINE, 0);
+	setenv("LESS_TERMCAP_ue", GIT_COLOR_RESET, 0);
+
+	/* Standout */
+	setenv("LESS_TERMCAP_so", GIT_COLOR_MAGENTA GIT_COLOR_REVERSE, 0);
+	setenv("LESS_TERMCAP_se", GIT_COLOR_RESET, 0);
+}
+
 static void exec_man_man(const char *path, const char *page)
 {
 	if (!path)
 		path = "man";
+
+	colorize_man();
 	execlp(path, "man", page, (char *)NULL);
 	warning_errno(_("failed to exec '%s'"), path);
 }
@@ -264,6 +288,7 @@ static void exec_man_man(const char *path, const char *page)
 static void exec_man_cmd(const char *cmd, const char *page)
 {
 	struct strbuf shell_cmd = STRBUF_INIT;
+	colorize_man();
 	strbuf_addf(&shell_cmd, "%s %s", cmd, page);
 	execl(SHELL_PATH, SHELL_PATH, "-c", shell_cmd.buf, (char *)NULL);
 	warning(_("failed to exec '%s'"), cmd);
@@ -372,7 +397,7 @@ static int git_help_config(const char *var, const char *value, void *cb)
 	if (starts_with(var, "man."))
 		return add_man_viewer_info(var, value);
 
-	return git_default_config(var, value, cb);
+	return git_color_default_config(var, value, cb);
 }
 
 static struct cmdnames main_cmds, other_cmds;
diff --git a/color.h b/color.h
index 98894d6a17..d012add4e8 100644
--- a/color.h
+++ b/color.h
@@ -51,6 +51,7 @@ struct strbuf;
 #define GIT_COLOR_FAINT		"\033[2m"
 #define GIT_COLOR_FAINT_ITALIC	"\033[2;3m"
 #define GIT_COLOR_REVERSE	"\033[7m"
+#define GIT_COLOR_UNDERLINE	"\033[4m"
 
 /* A special value meaning "no color selected" */
 #define GIT_COLOR_NIL "NIL"
-- 
2.31.1