Difference between revisions of "Patch and diff"

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This is a technique to
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This is an "advanced" technique for install scripts to
  
 
* Reduce the size of install scripts
 
* Reduce the size of install scripts

Revision as of 01:10, 11 September 2009

This is an "advanced" technique for install scripts to

  • Reduce the size of install scripts
  • Make them more forward compatible for the future
  • Make them more robust

The Idea

The idea is simple: install by hand, make changes to make it work, then compare against the pristine sources, generating a patch that later does automatically what you did by hand

  • Setup the app for installation as a webapp (say in html). Save a pristine copy as html.orign
  • Make changes in html/ only
  • Find out the diff of what you made:
        diff -r -N -b -u html.orig html > app-patch.diff
  • This then can go into the install script as follows:
        patch -p0 -E << EOF
        .... contents of app-patch.diff here ....
        EOF


Testing the patch ahead of time

It is strongly encouraged that you test the patch before attempting trial-and-error runs in the install script, which can be time consuming and error prone. This is basically simulating the install script applying the patch.

To do this, do this:

    mv html html.modified
    cp -a html.orig html
    mv html.orig html.pristine

(the last step is to prevent patch from accidentally patching html.orig)

then try your patch against html dir (which is now like the original):

    patch -p0 -E < app-patch.diff

Doing this will save you a lot of trial-and-error in the installer.

References