[PATCH] commit: explain basics in help text

[Adrian Buehlmann]

# HG changeset patch
# User Adrian Buehlmann <adrian at cadifra.com>
# Date 1342262730 -7200
# Node ID cad9193da3386127df17a2cfe558ce5f97bd6566
# Parent  8299a9ad48dd46ca7ce5a405f06fa2dd16f1b236
commit: explain basics in help text

If we explain the details about more complex concepts like --amend (using
notions like "parent"), we should probably first explain the basics.

diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -1221,6 +1221,23 @@
     centralized SCM, this operation is a local operation. See
     :hg:`push` for a way to actively distribute your changes.
 
+    Commit creates a new changeset which gets the parent revision of
+    the working directory as its parent changeset, or two parent
+    revisions, if the working directory contains an uncommitted merge
+    (use :hg:`parents` to see the parent revisions).
+
+    The newly created changeset will be set as the new parent revision
+    of the working directory (see the update command for switching the
+    parent revision of the working directory).
+
+    If you instead want to revert just one file, use :hg:`revert NAME`
+    or :hg:`revert --all` to revert all files to the contents they had
+    in the parent revision of the working directory.
+
+    To cancel an uncommitted merge (and lose all your changes), use
+    :hg:`update --clean .` ("." denotes the first parent revision of the
+    working directory, see :hg:`help revisions`).
+
     If a list of files is omitted, all changes reported by :hg:`status`
     will be committed.