Version 8 of Getting Started With Working On The Tcl/Tk Core

Updated 2011-03-16 19:14:55 by AK

The Tcl and Tk source repositories can be found at

The version control system used for these is Fossil.

The remainder of this page follows Fossil's generic Quickstart Guide , modified to suit Tcl/Tk development.

Installation

Prebuilt binaries for the major platforms (Linux, OSX, Windows, BSD) are available at http://www.fossil-scm.org/download.html Building it yourself is of course possible as well.

Getting Tcl and Tk Sources

Fossil works with repository files (a database with the project's complete history) and with checked-out local trees (the working directory you use to do your work). The workflow for Tcl and Tk looks like this:

First, clone the repository

fossil clone http://mirror1.tcl.tk/tcl tcl.fossil
fossil pull  http://core.tcl.tk/tcl -R tcl.fossil

fossil clone http://mirror1.tcl.tk/tk  tk.fossil
fossil pull  http://core.tcl.tk/tk  -R tk.fossil

We are using mirror1 because the repositories are large and http://core.tcl.tk/ is bandwidth-limited. To prevent fossil from remembering the wrong url for pushing we then follow this by pulls from the proper repository. This will also import all changes which were pushed while we were cloning around.

Make Ready For Work

Then create local checkouts to work with (using Tcl as example):

mkdir /somewhere/tcl
cd    /somewhere/tcl
fossil open /wherever/you/have/tcl.fossil

Now you have the most recent revision of Tcl's trunk (ex-CVS HEAD) in the directory. Hacking can commence.

Working In Branches

To fix issues in a specific branch, for example "core-8-5-branch", we have to create a local checkout which contains the sources of said branch. We can do this in two ways:

For one, create a new checkout and tell it the branch put into the checkout:

mkdir /somewhere/tcl-core-8-5-branch
cd    /somewhere/tcl-core-8-5-branch
fossil open /wherever/you/have/tcl.fossil core-8-5-branch

For two, reuse an existing checkout and switch it over to the desired branch

fossil update core-8-5-branch

The set of open branches can be discovered by invoking

fossil branch list

from within a checkout, or via

fossil branch list -R /wherever/you/have/tcl.fossil

if no checkout is available.

Porting Forward

When fixing an issue start doing that at the oldest branch you wish to support. When the fix is done sequentially merge it up to the newer branches, following a stair-case pattern.

For example, start the fix in "core-8-4-branch", after committing merge 8.4 to "core-8-5-branch", and lastly, merge 8.5 to trunk. Do not follow a star-pattern where the fix is directly merged from 8.4 to trunk. This messes up the ancestor-selection logic of future merges.

# In core-8-4-branch
... develop the fix
fossil commit ...

# Step I, merge up to 8.5
fossil update core-8-5-branch
fossil merge core-8-4-branch
... fix conflicts, if any
fossil commit ...

# Step II, merge up to 8.6 aka trunk
fossil update trunk
fossil merge core-8-5-branch
... fix conflicts, if any
fossil commit ...

Porting Backward

When fixing a bug it is not always clear in the beginning what the oldest branch is, to support. This leaves us later with the necessity of porting a change backward, making the staircase pattern impossible. In that case cherry-pick the change to apply in the older branch. Assuming our fix is VERSION, and has to go into 8.4:

fossil update core-8-4-branch
fossil merge --cherrypick VERSION
... fix conflicts, if any
fossil commit

TODO: Guidelines for use of branches (vs direct commit to trunk, etc.).

Pushing Changes

TODO

More Information

For those which have worked on the core before, using CVS, please also see the Fossil vs CVS Commands.