# 
# 
# patch "database.cc"
#  from [a65fbb52f8ad90194b9c195ee5e3c16e2113e5e9]
#    to [cac4ab9d4b50bd45c5888e84619bc6f342570367]
# 
# patch "project.cc"
#  from [106438500b4c6e9b1c2a742180557ca6c8f14840]
#    to [3a69d5eebcacb3ab5625a49dc98edf9979e7b46c]
# 
# patch "project.hh"
#  from [a37c5c9c535fdf22e8a41c3c4ef1cb8b8d8a12e0]
#    to [3a2f56c73b1467f8c3b8c6be8800f741d3a7430e]
# 
# patch "rev_height.cc"
#  from [82e46ae37bc2d01fa172d30bdf262e2479b8c185]
#    to [4c461f499aa31bdb99de01284ef879055eae47b4]
# 
# patch "rev_height.hh"
#  from [1317c1deae79d292e794943a64a604c22e008122]
#    to [cd31dbcb051c6a2181c971654f34ededb32a70c5]
# 
# patch "revision.hh"
#  from [13ef420b76868de35dca3208102304daa2d4593e]
#    to [b11a0ac769526e664b296e1ac9e71f1dd0ff01c8]
# 
# patch "schema_migration.cc"
#  from [703c3ecf0e220921ef5165203a1f561fb71ac875]
#    to [9ae3618fcf9b145df665c4a8e1bbb1d09e85d7b0]
# 
============================================================
--- database.cc	a65fbb52f8ad90194b9c195ee5e3c16e2113e5e9
+++ database.cc	cac4ab9d4b50bd45c5888e84619bc6f342570367
@@ -1736,7 +1736,7 @@ database::get_rev_height(revision_id con
 {
   if (null_id(id))
     {
-      rev_height::root_height(height);
+      height = rev_height::root_height();
       return;
     }
 
@@ -1747,7 +1747,8 @@ database::get_rev_height(revision_id con
 
   I(res.size() == 1);
   
-  height.from_string(res[0][0]);
+  height = rev_height(res[0][0]);
+  I(height.valid());
 }
 
 void
@@ -1756,6 +1757,7 @@ database::put_rev_height(revision_id con
 {
   I(!null_id(id));
   I(revision_exists(id));
+  !(height.valid());
   
   execute(query("INSERT INTO heights VALUES(?, ?)")
           % text(id.inner()())
@@ -1890,7 +1892,7 @@ database::put_height_for_revision(revisi
       
       while(!found)
         {
-          parent.child_height(candidate, childnr);
+          candidate = parent.child_height(childnr);
           if (!has_rev_height(candidate))
             {
               found = true;
============================================================
--- project.cc	106438500b4c6e9b1c2a742180557ca6c8f14840
+++ project.cc	3a69d5eebcacb3ab5625a49dc98edf9979e7b46c
@@ -12,7 +12,7 @@
 
 #include <boost/date_time/gregorian/gregorian.hpp>
 
-
+using std::string;
 using std::set;
 using std::vector;
 
============================================================
--- project.hh	a37c5c9c535fdf22e8a41c3c4ef1cb8b8d8a12e0
+++ project.hh	3a2f56c73b1467f8c3b8c6be8800f741d3a7430e
@@ -6,6 +6,7 @@
 
 #include <map>
 #include <set>
+#include <string>
 
 #include "cert.hh"
 #include "outdated_indicator.hh"
@@ -49,7 +50,7 @@ public:
   void get_branch_heads(utf8 const & name, std::set<revision_id> & heads);
 
   outdated_indicator get_tags(std::set<tag_t> & tags);
-  void put_tag(revision_id const & id, string const & name, packet_consumer & pc);
+  void put_tag(revision_id const & id, std::string const & name, packet_consumer & pc);
 
   bool revision_is_in_branch(revision_id const & id, utf8 const & branch);
   void put_revision_in_branch(revision_id const & id,
============================================================
--- rev_height.cc	82e46ae37bc2d01fa172d30bdf262e2479b8c185
+++ rev_height.cc	4c461f499aa31bdb99de01284ef879055eae47b4
@@ -7,12 +7,9 @@
 // implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 // PURPOSE.
 
-#include <iostream>
-#include <string>
 #include <cstring>
 #include <sstream>
 
-#include "numeric_vocab.hh"
 #include "sanity.hh"
 #include "rev_height.hh"
 
@@ -35,18 +32,7 @@ using std::memcmp;
  * 
  */
 
-rev_height::rev_height() {}
-
-rev_height::rev_height(rev_height const & other)
-{
-  d = other.d;
-}
-
-void rev_height::from_string(string const & s)
-{
-  d = s;
-}
-
+// Comparisons
 bool rev_height::operator==(rev_height const & other) const
 {
   if (d.size() != other.d.size())
@@ -58,22 +44,18 @@ bool rev_height::operator<(rev_height co
 
 bool rev_height::operator<(rev_height const & other) const
 {
-  if (d.size() == other.d.size())
-    return (memcmp(d.data(), other.d.data(), d.size()) < 0);
-
-  if (d.size() < other.d.size())
-    return (memcmp(d.data(), other.d.data(), d.size()) <= 0);
-
-  // d.size() > other.d.size()
-  return (memcmp(d.data(), other.d.data(), other.d.size()) < 0);
+  int o = memcmp(d.data(), other.d.data(),
+                 std::min(d.size(), other.d.size()));
+  if (o != 0)
+    return o < 0;
+  else
+    return d.size() < other.d.size();
 }
 
-string const & rev_height::operator()() const
-{
-  return d;
-}
+// Internal manipulations
+size_t const width = sizeof(u32);
 
-u32 rev_height::read_at(size_t pos) const
+static u32 read_at(string const & d, size_t pos)
 {
   u32 value = 0;
   size_t first = width * pos;
@@ -87,7 +69,7 @@ u32 rev_height::read_at(size_t pos) cons
   return value;
 }
 
-void rev_height::write_at(size_t pos, u32 value)
+static void write_at(string & d, size_t pos, u32 value)
 {
   size_t first = width * pos;
   for (size_t i = first + width ; i > first;)
@@ -97,55 +79,50 @@ void rev_height::write_at(size_t pos, u3
     }
 }
 
-void rev_height::append(u32 value)
+static void append(string & d, u32 value)
 {
   d.resize(d.size() + width);   // make room
-  write_at(size() - 1, value);
+  write_at(d, d.size() - width, value);
 }
 
-void rev_height::clear()
+// Creating derived heights
+rev_height rev_height::child_height(u32 nr) const
 {
-  d.clear();
-}
+  string child = d;
 
-size_t rev_height::size() const
-{
-  return d.size() / width;
-}
-
-void rev_height::child_height(rev_height & child, u32 nr) const
-{
-  child.from_string(d);
-
   if (nr == 0)
     {
-      size_t pos = size() - 1;
-      u32 tmp = read_at(pos);
+      size_t pos = child.size() / width - 1;
+      u32 tmp = read_at(child, pos);
       I(tmp < std::numeric_limits<u32>::max());
-      child.write_at(pos, tmp + 1);
+      write_at(child, pos, tmp + 1);
     }
   else
     {
-      child.append(nr - 1);
-      child.append(0);
+      append(child, nr - 1);
+      append(child, 0);
     }
+  return rev_height(child);
 }
 
-void rev_height::root_height(rev_height & root)
+rev_height rev_height::root_height()
 {
-  root.clear();
-  root.append(0);
+  string root;
+  append(root, 0);
+  return rev_height(root);
 }
 
+// Human-readable output
 ostream & operator <<(ostream & os, rev_height const & h)
 {
   bool first(true);
+  string const & d(h());
 
-  for (size_t i = 0; i < h.size(); ++i)
+  for (size_t i = 0; i < d.size() / width; ++i)
     {
       if (!first)
 	os << '.';
-      os << h.read_at(i);
+      os << read_at(d, i);
       first = false;
     }
   return os;
@@ -166,4 +143,3 @@ void dump(rev_height const & h, string &
 // indent-tabs-mode: nil
 // End:
 // vim: et:sw=2:sts=2:ts=2:cino=>2s,{s,\:s,+s,t0,g0,^-2,e-2,n-2,p2s,(0,=s:
-
============================================================
--- rev_height.hh	1317c1deae79d292e794943a64a604c22e008122
+++ rev_height.hh	cd31dbcb051c6a2181c971654f34ededb32a70c5
@@ -10,58 +10,51 @@
 // implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 // PURPOSE.
 
-#include <iostream>
+#include <iosfwd>
 #include <string>
 #include "numeric_vocab.hh"
 
-using std::ostream;
-using std::string;
-
-
 class rev_height
 {
-  string d;
-  static size_t const width = sizeof(u32);
-  u32 read_at(size_t pos) const;
-  void write_at(size_t pos, u32 val);
-  void append(u32 val);
-  size_t size() const;
-  void clear();
+  std::string d;
+
 public:
-  rev_height();
-  rev_height(rev_height const & other);
-  void from_string(string const & s);
-  string const & operator()() const;
-  void child_height(rev_height & child, u32 nr) const;
-  static void root_height(rev_height & root);
+  rev_height() : d() {}
+  rev_height(rev_height const & other) : d(other.d) {}
+  explicit rev_height(std::string const & s) : d(s) {}
+  std::string const & operator()() const { return d; }
 
+  rev_height child_height(u32 nr) const;
+  static rev_height root_height();
+
+  bool valid() const { return d.size() > 0; }
+
   bool operator ==(rev_height const & other) const;
   bool operator < (rev_height const & other) const;
 
-  inline bool operator !=(rev_height const & other) const
+  bool operator !=(rev_height const & other) const
   {
     return !(*this == other);
   }
-  inline bool operator > (rev_height const & other) const
+  bool operator > (rev_height const & other) const
   {
     return other < *this;
   }
-  inline bool operator <=(rev_height const & other) const
+  bool operator <=(rev_height const & other) const
   {
     return !(other < *this);
   }
-  inline bool operator >=(rev_height const & other) const
+  bool operator >=(rev_height const & other) const
   {
     return !(*this < other);
   }
-  friend ostream & operator <<(ostream & os, rev_height const & h);
 };
 
-void dump(rev_height const & h, string & out);
+std::ostream & operator <<(std::ostream & os, rev_height const & h);
+void dump(rev_height const & h, std::string & out);
 
 #endif // __REV_HEIGHT_HH_
 
-
 // Local Variables:
 // mode: C++
 // fill-column: 76
@@ -69,4 +62,3 @@ void dump(rev_height const & h, string &
 // indent-tabs-mode: nil
 // End:
 // vim: et:sw=2:sts=2:ts=2:cino=>2s,{s,\:s,+s,t0,g0,^-2,e-2,n-2,p2s,(0,=s:
-
============================================================
--- revision.hh	13ef420b76868de35dca3208102304daa2d4593e
+++ revision.hh	b11a0ac769526e664b296e1ac9e71f1dd0ff01c8
@@ -214,7 +214,7 @@ make_restricted_revision(parent_map cons
                          node_restriction const & mask,
                          revision_t & rev,
                          cset & excluded,
-                         string const & cmd_name);
+                         std::string const & cmd_name);
 
 void
 build_changesets_from_manifest_ancestry(app_state & app);
============================================================
--- schema_migration.cc	703c3ecf0e220921ef5165203a1f561fb71ac875
+++ schema_migration.cc	9ae3618fcf9b145df665c4a8e1bbb1d09e85d7b0
@@ -18,6 +18,8 @@
 #include "transforms.hh"
 #include "ui.hh"
 
+using std::string;
+
 // this file knows how to migrate schema databases. the general strategy is
 // to hash each schema we ever use, and make a list of the SQL commands
 // required to get from one hash value to the next. when you do a