= Information for ClearCase/UCM Users =

== ClearCase/UCM Concepts ==

== Syncing with a Mercurial Repository ==
It's simple enough to have a stream in !ClearCase coexist with a Mercurial repository. All you need is to create a snapshot view on the stream in question. After the files are updated and on a local disk, turn the snapshot view into a Mercurial repository.

{{{
hg init
hg addremove
hg ci -m "Initial checkin"
}}}

From there you can push the repository anywhere you like. 

=== ClearCase to Hg ===
As you pick up updates via rebasing in !ClearCase and updating your snapshot view, {{{hg status}}} will tell you what is out of sync with your repository. {{{hg addremove}}} is a wonderful command to keep files in sync with respect to new files and deleted files. 

=== Hg to ClearCase ===
This is a little tougher. 

!ClearCase, quite incorrectly, likes to own the mode on files, and keeps them read-only until they're checked-out. To update from Hg, I do the following

{{{
# I use cygwin for this on win32
find . -type f | xargs chmod u+w
hg pull
hg up
}}}

From !ClearCase's perspective, you've just hijacked some files. If you update from !ClearCase using the gui, it will prompt you to check them out and check them in again. 

{{{
ct update -graphical
}}}

To batch process this is more difficult, and that doesn't even cover files being renamed, removed, added, etc. 

=== Another Alternative ===

If you can live with a one-way push from Mercurial into !ClearCase (i.e. if !ClearCase is your ultimate source of record, but all checkins happen in Mercurial), then you can also make this work with a dynamic view rather than a snapshot view.  The trick is to use the {{{clearfsimport}}} command to import your changes from Mercurial to !ClearCase.  

I've been refining the shell script shown below for a few years now.  It's not the prettiest thing in the world, but hopefully it will offer a decent starting point for others in the same boat as me.

To push code into !ClearCase takes two steps.  First, I clone my working repository into {{{/home/pronovic/mercurial/MyProject}}}.  Then, I run the script below.  The script takes {{{/home/pronovic/mercurial/MyProject}}} and pushes it into {{{/vobs/ken/MyProject}}}.  Mercurial is the source, and the import process adds and removes files as necessary to make the vob target match the Mercurial source.

You'll find that {{{clearfsimport}}} is kind of clunky.  The arguments are not really "source" and "target".  They're more like "source" and "target directory".  So, you really tell it: "please import {{{/home/pronovic/mercurial/MyProject}}} into {{{/vobs/ken}}}" and that ends up creating or modifying {{{/vobs/ken/MyProject}}}.

-- KennethPronovici

{{{
#!/bin/ksh

# Sync configuration
typeset -x MERCURIALDIR="/home/pronovic/mercurial"
typeset -x VOBDIR="/vobs/ken"
typeset -x SOURCE="${MERCURIALDIR}/MyProject"
typeset -x TARGET="${VOBDIR}/MyProject"
typeset -x COMMENT="$1"

# Script configuration
typeset -x IMPORT="/usr/atria/bin/clearfsimport"
typeset -x STANDARD_OPTIONS="-nsetevent -recurse -rmname"
typeset -x PREVIEW_OPTION="-preview"

# Handle commend line
if [[ $# -eq 1 ]]
then
   typeset -x PREVIEW="false"
   typeset -x COMMENT="$1"
   typeset -x OPTIONS="$STANDARD_OPTIONS"
elif [[ $# -eq 2 ]]
then
   if [[ "$1" != "--preview" ]]
   then
      print "Usage: sync-mercurial [--preview] comment"
      print "Syncs $SOURCE into $VOBDIR"
      exit 1
   fi

   print "*** Operating in preview mode..."

   typeset -x PREVIEW="true"
   typeset -x COMMENT="$2"
   typeset -x OPTIONS="$STANDARD_OPTIONS $PREVIEW_OPTION"
else
   print "Usage: sync-mercurial [--preview] comment"
   print "Syncs $SOURCE into $VOBDIR"
   exit 1
fi

# Invoke clearfsimport to get things into ClearCase
"$IMPORT" $OPTIONS -c "$COMMENT" "$SOURCE" "$VOBDIR" 

# Check that the two repositories are indeed equivalent
if [[ "$PREVIEW" != "true" ]]
then
   if [[ $(diff -Naur "$SOURCE" "$TARGET" | wc -l) -ne 0 ]]
   then
      print "Error: recursive diff yielded inconsistencies between source and target!"
      print "To compare, use 'diff -Naur $SOURCE $TARGET"
   fi
fi
}}}