These are some tips to help committers to keep our Subversion (SVN) repository clean. See also Committers FAQ and PMC FAQ.

We do not want to get too concerned about style, other than a few obvious things such as whitespace. Basically just follow the style that is already used by the files that you are working on. We loosely follow the Sun Java Style Guide.

Whitespace can cause big problems with SVN. If it is inconsistent, then diffs are very hard to follow - actual changes become lost in the noise of whitespace changes. Some developers use editors that attempt to automatically format the whitespace. The trouble is that if SVN files are inconsistent, some of those editors just make it worse.

The solution comes in two parts:

When a committer adds a new file, they need to ensure that the file has the correct line endings for their own operating system, and that either their SVN client automatically sets the EOL settings for the file based upon the file extension, or they must do:

is that some committers who have a proper editor should occasionally correct the whitespace across all SVN files, applying the following rules.

For all text files:

• Replace all tabs with spaces.
• No trailing whitespace.
• No MS-DOS line endings.
• Newline at end-of-file.
• Single whitespace between words.

For all Java source files, as for text files plus:

• Use 4-space indentation.

For all XML source files, as for text files plus:

• Use 2-space indentation.
• No whitespace at start-of-file.
• No whitespace at end-of-file (except of course a newline).

If you are on a UNIX system, when you receive a patch from a contributor on Windows then do a 'dos2unix'. If you are on a Windows system, then ensure that you have a proper SVN client (it is supposed to convert to UNIX line-endings when you commit).

Here is one UNIX way to find all plain-text files that have DOS line-endings (and maybe mixed line-endings). There seem to be many images and jar archives that contain carriage-returns, so to list only the plain-text files:

To instead find all files (including images and foreign jar archives) that have DOS line-endings:

Here is one way to find files that have any hidden control characters: find . -type f | xargs grep -l '[[:cntrl:]]'

Many of us have wasted time with a broken build due to xml validation errors. Would all committers please either use a proper xml editor or validate their xdocs with one of the following commands: