git-instaweb: Check that correct config file exists for (re)start

Currently start/restart does not generate any configuration files for
spawning a new instance.  This means that

  $ git instaweb --http=<server> --start

might pick up stale 'httpd.conf' file for a different web server
(e.g. for default lighttpd when requesting apache2).

This commit changes that, and makes git-instaweb generate web server
config file and/or gitweb config file if don't exists.

This required naming config files after the name of web server
(alternate solution would be to somehow mark for which web server was
config file generated).

Note that web servers that embed configuration in server script file,
namely webrick and plackup, and which delete "$conf" in their *_conf
function, would have their config (server script) always regenerated.

Note: this commit introduces a bit of code repetition (but only a few
lines).

Reported-by: Gurjeet Singh <singh.gurjeet@gmail.com>
Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Acked-by: Eric Wong <normalperson@yhbt.net>

Documentation/git-instaweb.txt

@@ -51,8 +51,8 @@ OPTIONS
 
 start::
 --start::
-	Start the httpd instance and exit.  This does not generate
-	any of the configuration files for spawning a new instance.
+	Start the httpd instance and exit.  Regenerate configuration files
+	as necessary for spawning a new instance.
 
 stop::
 --stop::
@@ -62,8 +62,8 @@ stop::
 
 restart::
 --restart::
-	Restart the httpd instance and exit.  This does not generate
-	any of the configuration files for spawning a new instance.
+	Restart the httpd instance and exit.  Regenerate configuration files
+	as necessary for spawning a new instance.
 
 CONFIGURATION
 -------------

git-instaweb.sh

@@ -99,6 +99,12 @@ start_httpd () {
 
 	# here $httpd should have a meaningful value
 	resolve_full_httpd
+	mkdir -p "$fqgitdir/gitweb/$httpd_only"
+	conf="$fqgitdir/gitweb/$httpd_only.conf"
+
+	# generate correct config file if it doesn't exist
+	test -f "$conf" || configure_httpd
+	test -f "$fqgitdir/gitweb/gitweb_config.perl" || gitweb_conf
 
 	# don't quote $full_httpd, there can be arguments to it (-f)
 	case "$httpd" in
@@ -628,6 +634,7 @@ gitweb_conf
 
 resolve_full_httpd
 mkdir -p "$fqgitdir/gitweb/$httpd_only"
+conf="$fqgitdir/gitweb/$httpd_only.conf"
 
 configure_httpd