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+
+---------------------------------
+Version Control using Hg  Part 3
+---------------------------------
+
+.. Prerequisites
+.. -------------
+
+.. Version Control with hg - Part 1,2
+
+.. Author : Primal Pappachan
+   Internal Reviewer :
+   Date: Jan 27, 2012
+   
+   
+--------
+Script
+--------
+
+.. L1
+
+*{{{ Show the first slide containing title, name of the production team along
+with the logo of MHRD}}}*
+
+.. R1
+
+Hello friends and welcome to the tutorial on 'Version Control with Hg' 
+
+.. L2
+
+*{{{Show the slide 'Prerequisite'}}}*
+
+.. R2
+
+Please make sure that you have gone through the following tutorials before you
+continue on this tutorial
+
+.. L3
+
+*{{{Show the slide containing the objectives}}}*
+
+.. R3
+
+At the end of this tutorial you will be able to
+
+1. Learn how to view and revert changes made to files in a repository.
+
+#. Learn how to share repositories and deal with simultaneous conflicting change
+
+.. L4
+
+*{{{Show the slide 'Operational overhead?'}}}*
+
+.. R4 
+
+Let's first try to find out why we should commit inspite of the additional
+operational costs and loss of time?
+
+.. L4
+
+*{{{Show the slide 'Revert Changes'}}}*
+
+.. R4
+
+While you were wondering, let's say your friend walks in and together you make
+a lot of changes. 1. You replace all the occurrences of & in chapter1.txt with
+and. 2. You delete the chapter3.txt file.
+
+.. L5 
+
+``$ rm chapter3.txt``
+
+``$ hg st``
+
+``M chapter1.txt``
+
+``! chapter3.txt``
+
+.. R6
+
+But after a while, you realize that these changes are unwarranted. You want to
+go back to the previous state, undoing all the changes that you made, after
+your friend arrived.
+
+The undo in your editor may allow undoing some changes(if you haven't closed it
+after making the changes) but there's no way of getting back deleted files
+using your editor. That's where mercurial comes to the rescue.
+
+We shall use the revert command of hg to undo all the changes after the last
+commit. If we want to undo all the changes, we use the revert command with the
+--all argument, else use revert command with specific filename as argument.
+
+.. L5
+
+``$ hg revert --all``
+
+``reverting chapter1.txt``
+
+``reverting chapter3.txt``
+
+``$ hg st``
+
+``? chapter1.txt.orig``
+
+``$ ls``
+
+``chapter1.txt  chapter1.txt.orig  chapter2.txt  chapter3.txt``
+
+.. R5
+
+After running this command, you can see that all deleted files have been
+restored. But hg has generated new files with .orig extension.  Mercurial
+actually doesn't like  to delete any of the changes that you have made. So, it
+makes a back-up of the already existing files in the present state and gives
+you back the old file.
+
+If we now decide, that we want to redo the changes that we had done to the
+existing file, we can just overwrite it with the backed up file. 
+
+.. L6
+
+``$ mv chapter1.txt.orig chapter1.txt``
+
+``$ hg st``
+
+``M chapter1.txt``
+
+.. L7
+
+``{{{Show the slide 'Viewing Changes'}}}``
+
+.. R6
+
+Let's say we now want to commit these changes, but we are not sure of all the
+changes that we have made to the file, since it's been a while after we made
+the changes. We could use the diff command to see all the changes that have
+been made in the file.
+
+.. L8
+
+``$ hg diff``
+
+.. R7
+
+You see some cryptic output, but it's essentially giving you the list of
+changes made to the file. All the lines that were deleted are preceded by a -
+and all the new-lines are preceded by a +. You can see that the & occurrences
+have been replaces with and. 
+
+We should note here that, the diff wouldn't make much sense, if we had some
+binary files like .jpg or .pdf files. We would see some gibberish in the
+output. Let's now commit this change.
+
+.. L9
+
+``$hg commit``
+
+``$hg log``
+
+.. R8
+
+We can pass an additional argument, -v or --verbose, to hg log to get the whole
+commit message, instead of just the summary.
+
+.. L10
+
+``$hg log -v``
+
+.. R9
+
+Also, we are not always, interested to see the whole history of the project. It
+would often suffice to see the last few commits.
+
+.. L11
+
+``$ hg log -v -l3``
+
+.. R10
+
+To limit the output of hg log, we could use the -l or --limit argument. Now it
+will print only last three commits.
+
+.. L12
+
+*{{{Show the slide 'Revision Numbering'}}}*
+
+.. R11
+
+Often, the level of detail provided by the commit messages is also not enough.
+We would want to see what exactly changed with a commit, probably as a diff. We
+could do that using revision numbers. 
+
+Use the log command to get a brief description of all the changes made, by
+showing us the summary line of all the commits. Look at the changeset line in
+the output of the command. It shows a number followed by a semi-colon and some
+long hexa-decimal string. The number is called the revision number. It is an
+identifier for the commit, and can be along with various commands to specify
+the revision number, if required. 
+
+.. L13
+
+*{{{Show the slide  'Using revision numbers'}}}*
+
+
+.. R12
+
+The revision number can also be passed as an argument to many commands. Let's
+say we wish to see the changes between revision 1 and revision 2. We shall use
+the diff command to do this.
+
+.. L14
+
+``$ hg diff -r1 -r2``
+
+.. R13
+
+The diff command takes two revision numbers as arguments and gives the changes
+made from revision in the first argument to revision in the second argument.
+
+.. R14
+
+It can be passed to other commands as well. For instance, we can check the logs
+of the very first commit, by saying
+
+.. L15
+
+``$ hg log -r0``
+
+.. R15
+
+You could also specify a range of commits whose logs you would like to see.
+Say, we would like to see the last two commits,
+
+.. L16
+
+``$ hg log -r0:2``
+
+.. R16 
+
+To see changes made to a particular file, in the speciifed range of commits, 
+
+.. L17
+
+``$ hg log -r0:2 chapter2.txt``
+
+
+.. R17
+
+This brings us to the end of the tutorial. In this tutorial, we have
+seen,
+
+.. L18
+
+*{{{Show the 'summary' slide'}}}*
+
+.. R18
+
+In this tutorial, we have learnt to, 
+ #. Undo changes to the repository using hg revert,
+ #. View changes done to the repository using hg diff
+ #. Use revision numbers as arguments to different hg commands
+
+.. L19
+
+*{{{ Show self assessment questions slide }}}*
+
+.. R19
+
+Here are some self assessment questions for you to solve
+
+#. How to accomplish not saving backup files using hg revert command?
+#. Get the history of revisions 2 to 4 without having to list each revision? 
+#. Print the description and content of a change. Hint: Use --patch option
+
+.. L20
+
+*{{{ Solution of self assessment questions on slide }}}*
+
+.. R20
+
+And the answers,
+
+1. hg revert -C --no-backup
+
+2. hg log -r 2:4
+
+3. hg log -v -p -r 2
+
+.. L21
+
+*{{{ Show the Thank you slide }}}*
+
+.. R21
+
+Hope you have enjoyed this tutorial and found it useful. Feel free to play
+around with Mercurial and read the documentation given by hg help command. When
+you are ready to move on, please proceed to the third tutorial on 'Version
+Control using Hg'
+
+Thank you!