(This answer has been updated to match SVN 1.8 and 1.9's behaviour)

You have 2 questions:

Marking files as ignored:

By "ignored file" I mean the file won't appear in lists even as "unversioned": your SVN client will pretend the file doesn't exist at all in the filesystem.

Ignored files are specified by a "file pattern". The syntax and format of file patterns is explained in SVN's online documentation: http://svnbook.red-bean.com/nightly/en/svn.advanced.props.special.ignore.html "File Patterns in Subversion".

Subversion, as of version 1.8 (June 2013) and later, supports 3 different ways of specifying file patterns. Here's a summary with examples:

1 - Runtime Configuration Area - global-ignores option:

• This is a client-side only setting, so your global-ignores list won't be shared by other users, and it applies to all repos you checkout onto your computer.
• This setting is defined in your Runtime Configuration Area file:
  • Windows (file-based) - C:\Users\{you}\AppData\Roaming\Subversion\config
  • Windows (registry-based) - Software\Tigris.org\Subversion\Config\Miscellany\global-ignores in both HKLM and HKCU.
  • Linux/Unix - ~/.subversion/config

2 - The svn:ignore property, which is set on directories (not files):

• This is stored within the repo, so other users will have the same ignore files. Similar to how .gitignore works.
• svn:ignore is applied to directories and is non-recursive or inherited. Any file or immediate subdirectory of the parent directory that matches the File Pattern will be excluded.

• While SVN 1.8 adds the concept of "inherited properties", the svn:ignore property itself is ignored in non-immediate descendant directories:

  cd ~/myRepoRoot                             # Open an existing repo.
  echo "foo" > "ignoreThis.txt"                # Create a file called "ignoreThis.txt".
  
  svn status                                  # Check to see if the file is ignored or not.
  > ?    ./ignoreThis.txt
  > 1 unversioned file                        # ...it is NOT currently ignored.
  
  svn propset svn:ignore "ignoreThis.txt" .   # Apply the svn:ignore property to the "myRepoRoot" directory.
  svn status
  > 0 unversioned files                       # ...but now the file is ignored!
  
  cd subdirectory                             # now open a subdirectory.
  echo "foo" > "ignoreThis.txt"                # create another file named "ignoreThis.txt".
  
  svn status
  > ?    ./subdirectory/ignoreThis.txt        # ...and is is NOT ignored!
  > 1 unversioned file
  

  (So the file ./subdirectory/ignoreThis is not ignored, even though "ignoreThis.txt" is applied on the . repo root).

• Therefore, to apply an ignore list recursively you must use svn propset svn:ignore <filePattern> . --recursive.

  • This will create a copy of the property on every subdirectory.
  • If the <filePattern> value is different in a child directory then the child's value completely overrides the parents, so there is no "additive" effect.
  • So if you change the <filePattern> on the root ., then you must change it with --recursive to overwrite it on the child and descendant directories.

• I note that the command-line syntax is counter-intuitive.

  • I started-off assuming that you would ignore a file in SVN by typing something like svn ignore pathToFileToIgnore.txt however this is not how SVN's ignore feature works.

3- The svn:global-ignores property. Requires SVN 1.8 (June 2013):

• This is similar to svn:ignore, except it makes use of SVN 1.8's "inherited properties" feature.
• Compare to svn:ignore, the file pattern is automatically applied in every descendant directory (not just immediate children).
  • This means that is unnecessary to set svn:global-ignores with the --recursive flag, as inherited ignore file patterns are automatically applied as they're inherited.

• Running the same set of commands as in the previous example, but using svn:global-ignores instead:

  cd ~/myRepoRoot                                    # Open an existing repo
  echo "foo" > "ignoreThis.txt"                       # Create a file called "ignoreThis.txt"
  svn status                                         # Check to see if the file is ignored or not
  > ?    ./ignoreThis.txt
  > 1 unversioned file                               # ...it is NOT currently ignored
  
  svn propset svn:global-ignores "ignoreThis.txt" .
  svn status
  > 0 unversioned files                              # ...but now the file is ignored!
  
  cd subdirectory                                    # now open a subdirectory
  echo "foo" > "ignoreThis.txt"                       # create another file named "ignoreThis.txt"
  svn status
  > 0 unversioned files                              # the file is ignored here too!
  

For TortoiseSVN users:

This whole arrangement was confusing for me, because TortoiseSVN's terminology (as used in their Windows Explorer menu system) was initially misleading to me - I was unsure what the significance of the Ignore menu's "Add recursively", "Add *" and "Add " options. I hope this post explains how the Ignore feature ties-in to the SVN Properties feature. That said, I suggest using the command-line to set ignored files so you get a feel for how it works instead of using the GUI, and only using the GUI to manipulate properties after you're comfortable with the command-line.

Listing files that are ignored:

The command svn status will hide ignored files (that is, files that match an RGA global-ignores pattern, or match an immediate parent directory's svn:ignore pattern or match any ancesor directory's svn:global-ignores pattern.

Use the --no-ignore option to see those files listed. Ignored files have a status of I, then pipe the output to grep to only show lines starting with "I".

The command is:

svn status --no-ignore | grep "^I"

For example:

svn status
> ? foo                             # An unversioned file
> M modifiedFile.txt                # A versioned file that has been modified

svn status --no-ignore
> ? foo                             # An unversioned file
> I ignoreThis.txt                  # A file matching an svn:ignore pattern
> M modifiedFile.txt                # A versioned file that has been modified

svn status --no-ignore | grep "^I"
> I ignoreThis.txt                  # A file matching an svn:ignore pattern

ta-da!

The simple answer is that you svn export the file instead of checking it out.

But that might not be what you want. You might want to work on the file and check it back in, without having to download GB of junk you don't need.

If you have Subversion 1.5+, then do a sparse checkout:

svn checkout <url_of_big_dir> <target> --depth empty
cd <target>
svn up <file_you_want>

For an older version of SVN, you might benefit from the following:

• Checkout the directory using a revision back in the distant past, when it was less full of junk you don't need.
• Update the file you want, to create a mixed revision. This works even if the file didn't exist in the revision you checked out.
• Profit!

An alternative (for instance if the directory has too much junk right from the revision in which it was created) is to do a URL->URL copy of the file you want into a new place in the repository (effectively this is a working branch of the file). Check out that directory and do your modifications.

I'm not sure whether you can then merge your modified copy back entirely in the repository without a working copy of the target - I've never needed to. If so then do that.

If not then unfortunately you may have to find someone else who does have the whole directory checked out and get them to do it. Or maybe by the time you've made your modifications, the rest of it will have finished downloading...