opencvs: properly fix revision lookups

[Joris Vink]

Properly perform a revision lookup so update -r actually
works again, as a bonus throw a more correct error when
the revision could not be found.

(not on list, cc me)

.joris

Index: rcs.c
===================================================================
RCS file: /cvs/src/usr.bin/cvs/rcs.c,v
retrieving revision 1.312
diff -u -p -u -r1.312 rcs.c
--- rcs.c       16 Jan 2015 06:40:07 -0000      1.312
+++ rcs.c       12 Feb 2015 20:07:49 -0000
@@ -1821,17 +1821,13 @@ rcs_rev_getlines(RCSFILE *rfp, RCSNUM *f
 
 again:
        for (;;) {
+               if (rdp == NULL)
+                       break;
+
                if (rdp->rd_next->rn_len != 0) {
                        trdp = rcs_findrev(rfp, rdp->rd_next);
                        if (trdp == NULL)
                                fatal("failed to grab next revision");
-               } else {
-                       /*
-                        * XXX Fail, although the caller does not always do the
-                        * right thing (eg cvs diff when the tree is ahead of
-                        * the repository).
-                        */
-                       break;
                }
 
                if (rdp->rd_tlen == 0) {
@@ -1882,7 +1878,7 @@ again:
        }
 
 next:
-       if (!rcsnum_differ(rdp->rd_num, frev))
+       if (rdp == NULL || !rcsnum_differ(rdp->rd_num, frev))
                done = 1;
 
        if (RCSNUM_ISBRANCHREV(frev) && done != 1) {
@@ -2071,6 +2067,7 @@ rcs_rev_getbuf(RCSFILE *rfp, RCSNUM *rev
        struct rcs_delta *rdp;
        struct rcs_lines *lines;
        struct rcs_line *lp, *nlp;
+       char version[RCSNUM_MAXSTR];
        BUF *bp;
 
        rdp = NULL;
@@ -2083,8 +2080,12 @@ rcs_rev_getbuf(RCSFILE *rfp, RCSNUM *rev
                expmode = rcs_kwexp_get(rfp);
 
                if (!(expmode & RCS_KWEXP_NONE)) {
-                       if ((rdp = rcs_findrev(rfp, rev)) == NULL)
-                               fatal("could not fetch revision");
+                       if ((rdp = rcs_findrev(rfp, rev)) == NULL) {
+                               rcsnum_tostr(rev, version, sizeof(version));
+                               fatal("could not find desired version %s in %s",
+                                   version, rfp->rf_path);
+                       }
+
                        expand = 1;
                }
        }