chg: handle pager request client-side

This patch implements the simple S-channel pager handling at chg
client-side.

Note: It does not deal with environ and cwd currently for simplicity, which
will be fixed later.

contrib/chg/Makefile

@@ -25,7 +25,7 b' all: $(TARGET)'
 	$(CC) $(LDFLAGS) -o $@ $(OBJS)
 
 chg.o: hgclient.h procutil.h util.h
-hgclient.o: hgclient.h util.h
+hgclient.o: hgclient.h procutil.h util.h
 procutil.o: procutil.h util.h
 util.o: util.h
 

contrib/chg/hgclient.c

@@ -23,6 +23,7 b''
 #include <unistd.h>
 
 #include "hgclient.h"
+#include "procutil.h"
 #include "util.h"
 
 enum {
@@ -71,6 +72,8 b' struct hgclient_tag_ {'
 
 static const size_t defaultdatasize = 4096;
 
+static void attachio(hgclient_t *hgc);
+
 static void initcontext(context_t *ctx)
 {
 	ctx->ch = '\0';
@@ -248,6 +251,13 b' static void handlesystemrequest(hgclient'
 		memcpy(ctx->data, &r_n, sizeof(r_n));
 		ctx->datasize = sizeof(r_n);
 		writeblock(hgc);
+	} else if (strcmp(args[0], "pager") == 0) {
+		setuppager(args[1]);
+		if (hgc->capflags & CAP_ATTACHIO)
+			attachio(hgc);
+		/* unblock the server */
+		static const char emptycmd[] = "\n";
+		sendall(hgc->sockfd, emptycmd, sizeof(emptycmd) - 1);
 	} else {
 		abortmsg("unknown type in system request: %s", args[0]);
 	}