Default GIT_COMMITTER_NAME to login name in recieve-pack.

If GIT_COMMITTER_NAME is not available in receive-pack but reflogs
are enabled we would normally die out with an error message asking
the user to correct their environment settings.

Now that reflogs are enabled by default in (what we guessed to be)
non-bare Git repositories this may cause problems for some users
who don't have their full name in the gecos field and who don't
have access to the remote system to correct the problem.

So rather than die()'ing out in receive-pack when we try to log a
ref change and have no committer name we default to the username,
as obtained from the host's password database.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

cache.h

@@ -309,6 +309,7 @@ void datestamp(char *buf, int bufsize);
 unsigned long approxidate(const char *);
 
 extern int setup_ident(void);
+extern void ignore_missing_committer_name();
 extern const char *git_author_info(int);
 extern const char *git_committer_info(int);
 

ident.c

@@ -221,3 +221,18 @@ const char *git_committer_info(int error_on_no_name)
 			 getenv("GIT_COMMITTER_DATE"),
 			 error_on_no_name);
 }
+
+void ignore_missing_committer_name()
+{
+	/* If we did not get a name from the user's gecos entry then
+	 * git_default_name is empty; so instead load the username
+	 * into it as a 'good enough for now' approximation of who
+	 * this user is.
+	 */
+	if (!*git_default_name) {
+		struct passwd *pw = getpwuid(getuid());
+		if (!pw)
+			die("You don't exist. Go away!");
+		strlcpy(git_default_name, pw->pw_name, sizeof(git_default_name));
+	}
+}

receive-pack.c

@@ -420,6 +420,8 @@ int main(int argc, char **argv)
 		die("'%s': unable to chdir or not a git archive", dir);
 
 	setup_ident();
+	/* don't die if gecos is empty */
+	ignore_missing_committer_name();
 	git_config(receive_pack_config);
 
 	write_head_info();