SVN Branch/Merge tutorial

NOTE: THE EXAMPLES ARE DONE ON ALFS PC, AND ANY DIRECTORY NAMES CONTAINING “alfg” ARE NOT VALID ON YOUR PC!! USE SOME NAMES WHICH MAKE SENSE ON YOUR PC!

PART 1 : Create a repository and put a file there

CREATE A REPOSITORY

alfg@pc4400:~$svnadmin create $HOME/svnrepos

CREATE A WORKING DIRECTORY WITH CODE

alfg@pc4400:~$mkdir $HOME/testproject

Use the following as the file test.F90:

program test
implicit none
real, parameter :: a=4.0
real, parameter :: b=5.0
print*, "a is " , a
print*, "b is " , b
print*, "a+b is " , a+b
end program test

CD TO WORKING DIRECTORY AND VERIFY THAT THE TEST FILE IS THERE

alfg@pc4400:~/testproject$ ls -l
total 4
-rw-rw-r-- 1 alfg alfg 166 Dec 6 14:51 test.F90

CD TO THE FRESHLY CREATED REPOSITORY AND CREATE “testproject”

alfg@pc4400:~/svnrepos$ svnadmin create testproject

IMPORT YOUR WORKING-DIRECTORY TO THE REPOSITORY

alfg@pc4400:~$svn import $HOME/testproject/ file://$HOME/svnrepos/testproject/trunk -m "Initial version of testproject"

MAKE A BRANCHES-DIRECTORY

alfg@pc4400:~$svn mkdir file://$HOME/svnrepos/testproject/branches/ -m "created branches directory"

==>YOU NOW HAVE A REPOSITORY CONTAINING TRUNK AND (EMPTY) BRANCHES DIRECTORY. YOU CAN START TO USE IT

PART 2: Create a working directory for two developers

alfg@pc4400:~$mkdir twoDevelopers
alfg@pc4400:~$cd twoDevelopers

CHECK OUT TRUNK FOR ONE DEVELOPER

alfg@pc4400:~$svn checkout file://$HOME/svnrepos/testproject/trunk trunk
alfg@pc4400:~$cd trunk

CREATE A BRANCH BASED ON TRUNK

alfg@pc4400:~/twoDevelopers/trunk$ svn copy file://$HOME/svnrepos/testproject/trunk file://$HOME/svnrepos/testproject/branches/aBranch -m "created branch aBranch"

CD BACK ONE STEP AND CHECK OUT THE BRANCH FOR THE OTHER DEVELOPER

alfg@pc4400:~/twoDevelopers$ svn checkout file://$HOME/svnrepos/testproject/branches/aBranch aBranch

==> THE DIRECTORY “TWODEVELOPERS” NOW HAS TWO DIRECTORIES, ONE WITH TRUNK AND ONE WITH A BRANCH VERIFY THAT THEY ARE THERE USING THE “LS” COMMAND

alfg@pc4400:~/twoDevelopers$ ls -trl
total 8
drwxrwxr-x 3 alfg alfg 4096 Dec 9 08:36 trunk
drwxrwxr-x 3 alfg alfg 4096 Dec 9 09:40 aBranch

PART 3: Create conflict in the file test.F90

EDIT FILE ON TRUNK

alfg@pc4400:~/twoDevelopers/trunk$ vim test.F90
alfg@pc4400:~/twoDevelopers/trunk$ svn commit -m "added hello"
alfg@pc4400:~/twoDevelopers/trunk$ svn update

EDIT FILE ON BRANCH

alfg@pc4400:~/twoDevelopers/aBranch$ vim test.F90
alfg@pc4400:~/twoDevelopers/aBranch$ svn commit -m "added Hi man"
alfg@pc4400:~/twoDevelopers/aBranch$ svn update

==> We have now created a conflict between the branch “aBranch” and “trunk”

alfg@pc4400:~/twoDevelopers$ diff aBranch/test.F90 trunk/test.F90
9c9
<	print*, "Hi Man! a+b is " , a+b
---
>	print*, "Hello a+b is " , a+b

PART 4: Test the merge dialog

TRY TO MERGE TRUNK INTO BRANCH

alfg@pc4400:~/twoDevelopers/aBranch$ svn merge file://$HOME/svnrepos/testproject/trunk

You will get the message that there is a conflict in file test.F90, you will have to resolve the conflict Push the “postpone” option to quit the merge dialog

UNDO THE MERGE WITH

alfg@pc4400:~/twoDevelopers/aBranch$ svn revert -R .

==> You have undone the merge, nothing has happened

alfg@pc4400:~/twoDevelopers/aBranch$ svn diff
alfg@pc4400:~/twoDevelopers/aBranch$

PART 5: Set up favourite editor as merge tool

1) Create a file somewhere in your pc, for example I use $HOME/bin/mergetoolscript.sh

For emacs users, the content of the script is:

#!/bin/sh
emacs -q --eval "(ediff-merge-files-with-ancestor "\"$2"\" \""$3"\" \""$1"\" nil \""$4"\")"

For vi users, the content of the script is:

#!/bin/sh
vim -d "+diffsplit $3" "+vert diffsplit $1" "+vert diffsplit $2" -o $4

2) Open your $HOME/.subversion/config file and replace the line with merge tool (NOTE THAT FULL PATH IS NEEDED. NO BLANK CHARACTERS AT BEGINNGING OF LINE!!)

merge-tool-cmd = /home/alfg/bin/mergetoolscript.sh

MAKE SURE SCRIPT IS EXECUTABLE

chmod +x $HOME/bin/mergetoolscript.sh

==> You should now have working merge tools. This will make merging EASY!!

PART 6: Go back to merge operation and use merge tool

* TUTORIAL PART 6: GO BACK TO MERGE OPERATION AND USE MERGE TOOL!!

alfg@pc4400:~/twoDevelopers/aBranch$ svn merge file://$HOME/svnrepos/testproject/trunk

type “s” to “show all options” and “l” to “launch external tool”.

==> emacs or vi should be invoked in “merge mode”

The vi script shows (your, ancestor, mine) on top and output below the emacs script shows (yours, mine) on top and merged version (including common ancestor) below

All editing should happen in the lowest part of the editor window

When done editing, save the file and quit the editor

When back in the merge-dialog, press “r” (resolved)

PART 7: Verify that you are happy with merge

alfg@pc4400:~/twoDevelopers/aBranch$ svn diff

Note how it is difficult to understand the diff ==> we need to configure a diff tool!

To configure a nice diff-viewer, you need to replace a line in your $HOME/.subversion/config. (use a file somewhere on your PC). The script is only TWO LINES long!!

diff-cmd = /home/alfg/bin/diffwrap.sh

The content of this script (only two lines) for emacs users can be:

#!/bin/sh
emacs --eval "(ediff-files "\"$6"\" \""$7"\" )"

(Use | (pipeline) key in the “ediff” dialog to toggle between vertical/horizontal diff view)

The content of this script for vi users can be

#!/bin/sh
vimdiff $6 $7

Verify the diff again using the diff viewer

alfg@pc4400:~/twoDevelopers/aBranch$ svn diff

When you are happy with the diffs, do

alfg@pc4400:~/twoDevelopers/aBranch$ svn commit -m "Successfully branched trunk to my branch"

==> DONE

PART 8: Merge back to trunk

After the conflict is resolved and committed from branch, go back to trunk

alfg@pc4400:~/twoDevelopers/trunk$ svn merge --reintegrate file://$HOME/svnrepos/testproject/branches/aBranch

alfg@pc4400:~/twoDevelopers/trunk$ svn commit -m "merged aBranch back to trunk"

==> Observe that you don't get any conflict this time. Svn knows that the conflict is already resolved.

Other important points

The merge is not completed until you commit!

You have to know if you are doing a reintegrate merge or a merge from trunk (see noresm wiki)

You can undo the merge with alfg@pc4400:~/twoDevelopers/aBranch$ svn revert -R .

When you have done a “reintegrate merge”, consider your branch dead! (remove it and create it again if needed)

If you insist on keeping reintegrated branches alive, there are two options:

Start using another version control system

Make sure you have latest svn version (version >= 1.7), Then read (and understand) http://svnbook.red-bean.com/en/1.7/svn.branchmerge.advanced.html#svn.branchmerge.advanced.reintegratetwice