Difference between revisions of "Diff and patch"

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-x".svn" -x"CVS" -x"core" -x"a.out"
 
-x".svn" -x"CVS" -x"core" -x"a.out"
 
"/home/user/project-ORIGINAL" "." > /tmp/changes.patch
 
"/home/user/project-ORIGINAL" "." > /tmp/changes.patch
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</pre>
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== diff two directory trees ==
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This will compare two directory trees for new, deleted, and modified files.
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<pre>
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diff -u -r -N /home/noah/bsp/rootfs.theirs /home/noah/bsp/rootfs.mine
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</pre>
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If you are generating a patch between an old version and a new version then the results will be smaller and more clear if you use the '''--unidirectional-new-file''' option instead of the '''-N''' option. Note that you must make sure you specify the '''old''' directory first and the '''new''' directory second.
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<pre>
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<pre>
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diff -u -r --unidirectional-new-file /home/noah/bsp/rootfs.old /home/noah/bsp/rootfs.new     
 
</pre>
 
</pre>

Revision as of 18:12, 8 March 2011

If you don't have svn write access to a project and want to submit a manual patch, the following notes should help. You made changes to many files in a project and you want to submit a patch to the maintainer of the project. First, find out if they want Context or Unified diffs. That will set the -c or -u option for diff. Go with -c when in doubt. You will use the -r option to recursively compare the ORIGINAL directory with the NEWER directory (the one with your changes). You can add many more -x options to exclude patterns of files that you do not want included in the patch. Usually you don't want to compare binaries or files generated by the build process (make).

cd /home/user/project-NEWER
diff -r -c -x"*.jpg" -x"*.png" -x"*.gif" -x"*.swp" \
-x"*.a" -x"*.so" -x"*.o" -x"*.pyc" -x"*.exe" -x"*.class" \
-x".svn" -x"CVS" -x"core" -x"a.out"
"/home/user/project-ORIGINAL" "." > /tmp/changes.patch

This will generate a patch file that you can mail to the project maintainer. They will then apply the patch as follows:

cd project-ORIGINAL
patch -p0 < /tmp/changes.patch

Note the -p0 option. Also note that the path to changes.patch will depend on where the maintainer stored it (/tmp/ is just an example).

Sometimes you and the maintainer will not be working from exactly the same ORIGINAL source. Patch can search around a fuzzy area of code and find where the context matches. In this case it can help to have more context for patch to work with. Use the "-C NUM" options instead of '-c':

diff -r -C 7 -x"*.jpg" -x"*.png" -x"*.gif" -x"*.swp" \
-x"*.a" -x"*.so" -x"*.o" -x"*.pyc" -x"*.exe" -x"*.class" \
-x".svn" -x"CVS" -x"core" -x"a.out"
"/home/user/project-ORIGINAL" "." > /tmp/changes.patch

diff two directory trees

This will compare two directory trees for new, deleted, and modified files.

diff -u -r -N /home/noah/bsp/rootfs.theirs /home/noah/bsp/rootfs.mine

If you are generating a patch between an old version and a new version then the results will be smaller and more clear if you use the --unidirectional-new-file option instead of the -N option. Note that you must make sure you specify the old directory first and the new directory second.

<pre>
diff -u -r --unidirectional-new-file /home/noah/bsp/rootfs.old /home/noah/bsp/rootfs.new