diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -2855,7 +2855,7 @@ def revert(ui, repo, *pats, **opts):
         wlock.release()
 
 def rollback(ui, repo, **opts):
-    """roll back the last transaction
+    """roll back the last transaction (dangerous)
 
     This command should be used with care. There is only one level of
     rollback, and there is no way to undo a rollback. It will also
@@ -2891,7 +2891,7 @@ def root(ui, repo):
     ui.write(repo.root + "\n")
 
 def serve(ui, repo, **opts):
-    """export the repository via HTTP
+    """start stand-alone webserver
 
     Start a local HTTP repository browser and pull server.
 
@@ -3316,7 +3316,7 @@ def unbundle(ui, repo, fname1, *fnames, 
     return postincoming(ui, repo, modheads, opts.get('update'), None)
 
 def update(ui, repo, node=None, rev=None, clean=False, date=None, check=False):
-    """update working directory
+    """update working directory (or switch revisions)
 
     Update the repository's working directory to the specified
     changeset.
diff --git a/tests/test-globalopts.out b/tests/test-globalopts.out
--- a/tests/test-globalopts.out
+++ b/tests/test-globalopts.out
@@ -186,9 +186,9 @@ list of commands:
  rename       rename files; equivalent of copy + remove
  resolve      various operations to help finish a merge
  revert       restore individual files or directories to an earlier state
- rollback     roll back the last transaction
+ rollback     roll back the last transaction (dangerous)
  root         print the root (top) of the current working directory
- serve        export the repository via HTTP
+ serve        start stand-alone webserver
  showconfig   show combined config settings from all hgrc files
  status       show changed files in the working directory
  summary      summarize working directory state
@@ -196,7 +196,7 @@ list of commands:
  tags         list repository tags
  tip          show the tip revision
  unbundle     apply one or more changegroup files
- update       update working directory
+ update       update working directory (or switch revisions)
  verify       verify the integrity of the repository
  version      output version and copyright information
 
@@ -255,9 +255,9 @@ list of commands:
  rename       rename files; equivalent of copy + remove
  resolve      various operations to help finish a merge
  revert       restore individual files or directories to an earlier state
- rollback     roll back the last transaction
+ rollback     roll back the last transaction (dangerous)
  root         print the root (top) of the current working directory
- serve        export the repository via HTTP
+ serve        start stand-alone webserver
  showconfig   show combined config settings from all hgrc files
  status       show changed files in the working directory
  summary      summarize working directory state
@@ -265,7 +265,7 @@ list of commands:
  tags         list repository tags
  tip          show the tip revision
  unbundle     apply one or more changegroup files
- update       update working directory
+ update       update working directory (or switch revisions)
  verify       verify the integrity of the repository
  version      output version and copyright information
 
diff --git a/tests/test-help.out b/tests/test-help.out
--- a/tests/test-help.out
+++ b/tests/test-help.out
@@ -15,10 +15,10 @@ basic commands:
  pull       pull changes from the specified source
  push       push changes to the specified destination
  remove     remove the specified files on the next commit
- serve      export the repository via HTTP
+ serve      start stand-alone webserver
  status     show changed files in the working directory
  summary    summarize working directory state
- update     update working directory
+ update     update working directory (or switch revisions)
 
 use "hg help" for the full list of commands or "hg -v" for details
  add        add the specified files on the next commit
@@ -34,10 +34,10 @@ use "hg help" for the full list of comma
  pull       pull changes from the specified source
  push       push changes to the specified destination
  remove     remove the specified files on the next commit
- serve      export the repository via HTTP
+ serve      start stand-alone webserver
  status     show changed files in the working directory
  summary    summarize working directory state
- update     update working directory
+ update     update working directory (or switch revisions)
 Mercurial Distributed SCM
 
 list of commands:
@@ -79,9 +79,9 @@ list of commands:
  rename       rename files; equivalent of copy + remove
  resolve      various operations to help finish a merge
  revert       restore individual files or directories to an earlier state
- rollback     roll back the last transaction
+ rollback     roll back the last transaction (dangerous)
  root         print the root (top) of the current working directory
- serve        export the repository via HTTP
+ serve        start stand-alone webserver
  showconfig   show combined config settings from all hgrc files
  status       show changed files in the working directory
  summary      summarize working directory state
@@ -89,7 +89,7 @@ list of commands:
  tags         list repository tags
  tip          show the tip revision
  unbundle     apply one or more changegroup files
- update       update working directory
+ update       update working directory (or switch revisions)
  verify       verify the integrity of the repository
  version      output version and copyright information
 
@@ -144,9 +144,9 @@ use "hg -v help" to show aliases and glo
  rename       rename files; equivalent of copy + remove
  resolve      various operations to help finish a merge
  revert       restore individual files or directories to an earlier state
- rollback     roll back the last transaction
+ rollback     roll back the last transaction (dangerous)
  root         print the root (top) of the current working directory
- serve        export the repository via HTTP
+ serve        start stand-alone webserver
  showconfig   show combined config settings from all hgrc files
  status       show changed files in the working directory
  summary      summarize working directory state
@@ -154,7 +154,7 @@ use "hg -v help" to show aliases and glo
  tags         list repository tags
  tip          show the tip revision
  unbundle     apply one or more changegroup files
- update       update working directory
+ update       update working directory (or switch revisions)
  verify       verify the integrity of the repository
  version      output version and copyright information
 
@@ -206,13 +206,13 @@ basic commands:
  remove, rm:
       remove the specified files on the next commit
  serve:
-      export the repository via HTTP
+      start stand-alone webserver
  status, st:
       show changed files in the working directory
  summary, sum:
       summarize working directory state
  update, up, checkout, co:
-      update working directory
+      update working directory (or switch revisions)
 
 global options:
  -R --repository      repository root directory or name of overlay bundle file
@@ -487,10 +487,10 @@ basic commands:
  pull       pull changes from the specified source
  push       push changes to the specified destination
  remove     remove the specified files on the next commit
- serve      export the repository via HTTP
+ serve      start stand-alone webserver
  status     show changed files in the working directory
  summary    summarize working directory state
- update     update working directory
+ update     update working directory (or switch revisions)
 
 use "hg help" for the full list of commands or "hg -v" for details
 hg: unknown command 'skjdfks'
@@ -511,10 +511,10 @@ basic commands:
  pull       pull changes from the specified source
  push       push changes to the specified destination
  remove     remove the specified files on the next commit
- serve      export the repository via HTTP
+ serve      start stand-alone webserver
  status     show changed files in the working directory
  summary    summarize working directory state
- update     update working directory
+ update     update working directory (or switch revisions)
 
 use "hg help" for the full list of commands or "hg -v" for details
 %% test command with no help text
@@ -565,9 +565,9 @@ list of commands:
  rename       rename files; equivalent of copy + remove
  resolve      various operations to help finish a merge
  revert       restore individual files or directories to an earlier state
- rollback     roll back the last transaction
+ rollback     roll back the last transaction (dangerous)
  root         print the root (top) of the current working directory
- serve        export the repository via HTTP
+ serve        start stand-alone webserver
  showconfig   show combined config settings from all hgrc files
  status       show changed files in the working directory
  summary      summarize working directory state
@@ -575,7 +575,7 @@ list of commands:
  tags         list repository tags
  tip          show the tip revision
  unbundle     apply one or more changegroup files
- update       update working directory
+ update       update working directory (or switch revisions)
  verify       verify the integrity of the repository
  version      output version and copyright information
 
diff --git a/tests/test-qrecord.out b/tests/test-qrecord.out
--- a/tests/test-qrecord.out
+++ b/tests/test-qrecord.out
@@ -17,10 +17,10 @@ basic commands:
  pull       pull changes from the specified source
  push       push changes to the specified destination
  remove     remove the specified files on the next commit
- serve      export the repository via HTTP
+ serve      start stand-alone webserver
  status     show changed files in the working directory
  summary    summarize working directory state
- update     update working directory
+ update     update working directory (or switch revisions)
 
 use "hg help" for the full list of commands or "hg -v" for details
 % help (mq present)
diff --git a/tests/test-strict.out b/tests/test-strict.out
--- a/tests/test-strict.out
+++ b/tests/test-strict.out
@@ -18,10 +18,10 @@ basic commands:
  pull       pull changes from the specified source
  push       push changes to the specified destination
  remove     remove the specified files on the next commit
- serve      export the repository via HTTP
+ serve      start stand-alone webserver
  status     show changed files in the working directory
  summary    summarize working directory state
- update     update working directory
+ update     update working directory (or switch revisions)
 
 use "hg help" for the full list of commands or "hg -v" for details
 0: a