In any given working copy, there is a good chance that alongside all those versioned files and directories are other files and directories that are neither versioned nor intended to be. Text editors litter directories with backup files. Software compilers generate intermediate—or even final—files that you typically wouldn't bother to version. And users themselves drop various other files and directories wherever they see fit, often in version control working copies.
It's ludicrous to expect Subversion working copies to be somehow impervious to this kind of clutter and impurity. In fact, Subversion counts it as a feature that its working copies are just typical directories, just like unversioned trees. But these not-to-be-versioned files and directories can cause some annoyance for Subversion users. For example, because the svn add and svn import commands act recursively by default and don't know which files in a given tree you do and don't wish to version, it's easy to accidentally add stuff to version control that you didn't mean to. And because svn status reports, by default, every item of interest in a working copy—including unversioned files and directories—its output can get quite noisy where many of these things exist.
So Subversion provides two ways for telling it which files you would prefer for it to simply disregard. One of the ways involves the use of Subversion's runtime configuration system (see “运行配置区”一节), and therefore applies to all the Subversion operations that make use of that runtime configuration—generally those performed on a particular computer or by a particular user of a computer. The other way makes use of Subversion's directory property support and is more tightly bound to the versioned tree itself, and therefore affects everyone who has a working copy of that tree. Both of the mechanisms use file patterns (strings of literal and special wildcard characters used to match against filenames) to decide which files to ignore.
The Subversion runtime configuration system provides an
option, global-ignores, whose value is a
whitespace-delimited collection of file patterns. The
Subversion client checks these patterns against the names of the
files that are candidates for addition to version control, as
well as to unversioned files that the svn
status command notices. If any file's name matches
one of the patterns, Subversion will basically act as if the
file didn't exist at all. This is really useful for the kinds
of files that you almost never want to version, such as editor
backup files such as Emacs' *~ and
.*~ files.
When found on a versioned directory, the
svn:ignore property is expected to contain a
list of newline-delimited file patterns that Subversion should
use to determine ignorable objects in that same directory.
These patterns do not override those found in the
global-ignores runtime configuration option,
but are instead appended to that list. And it's worth noting
again that, unlike the global-ignores option,
the patterns found in the svn:ignore
property apply only to the directory on which that property is
set, and not to any of its subdirectories. The
svn:ignore property is a good way to tell
Subversion to ignore files that are likely to be present in
every user's working copy of that directory, such as compiler
output or—to use an example more appropriate to this
book—the HTML, PDF, or PostScript files generated as the
result of a conversion of some source DocBook XML files to a
more legible output format.
Subversion对于忽略文件模式的支持仅限于将未版本化文件和目录添加到版本控制时，如果一个文件已经在Subversion控制下，忽略模式机制不会再有效果，不要期望Subversion会阻止你提交一个符合忽略条件的修改—Subversion一直认为它是版本化的对象。
The global list of ignore patterns tends to be more a
matter of personal taste and ties more closely to a user's
particular tool chain than to the details of any particular
working copy's needs. So, the rest of this section will focus
on the svn:ignore property and its
uses.
假定你的svn status有如下输出：
$ svn status calc M calc/button.c ? calc/calculator ? calc/data.c ? calc/debug_log ? calc/debug_log.1 ? calc/debug_log.2.gz ? calc/debug_log.3.gz
In this example, you have made some property modifications
to button.c, but in your working copy, you
also have some unversioned files: the latest
calculator program that you've compiled
from your source code, a source file named
data.c, and a set of debugging output log
files. Now, you know that your build system always results in
the calculator program being generated.
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And you know that your test suite always leaves those debugging
log files lying around. These facts are true for all working
copies of this project, not just your own. And you know that
you aren't interested in seeing those things every time you run
svn status, and you are pretty sure that
nobody else is interested in them either. So you use
svn propedit svn:ignore calc to add some
ignore patterns to the calc directory. For
example, you might add this as the new value of the
svn:ignore property:
calculator debug_log*
当你添加完这些属性，你会在calc目录有一个本地修改，但是注意你的svn status输出有什么其他的不同：
$ svn status M calc M calc/button.c ? calc/data.c
Now, all that cruft is missing from the output! Your
calculator compiled program and all those
logfiles are still in your working copy; Subversion just isn't
constantly reminding you that they are present and unversioned.
And now with all the uninteresting noise removed from the
display, you are left with more intriguing items—such as
that source code file data.c that you
probably forgot to add to version control.
当然，不仅仅只有这种简略的工作拷贝状态输出，如果想查看被忽略的文件，可以使用Subversion的--no-ignore选项：
$ svn status --no-ignore M calc M calc/button.c I calc/calculator ? calc/data.c I calc/debug_log I calc/debug_log.1 I calc/debug_log.2.gz I calc/debug_log.3.gz
我们在前面提到过，svn add和svn import也会使用这个忽略模式列表，这两个操作都包括了询问Subversion来开始管理一组文件和目录。比强制用户挑拣目录树中那个文件要纳入版本控制的方式更好，Subversion使用忽略模式来检测那个文件不应该在大的迭代添加和导入操作中进入版本控制系统。再次说明，操作Subversion文件和目录时你可以使用--no-ignore选项忽略这个忽略列表。
Even if svn:ignore is set, you may run
into problems if you use shell wildcards in a command. Shell
wildcards are expanded into an explicit list of targets before
Subversion operates on them, so running svn
SUBCOMMAND * is just like
running svn SUBCOMMAND
file1 file2 file3 …. In the case of the
svn add command, this has an effect similar
to passing the --no-ignore option. So
instead of using a wildcard, use svn add --force
. to do a bulk scheduling of unversioned things for
addition. The explicit target will ensure that the current
directory isn't overlooked because of being already under
version control, and the --force option will
cause Subversion to crawl through that directory, adding
unversioned files while still honoring the
svn:ignore property and
global-ignores runtime configuration
variable. Be sure to also provide the --depth
files option to the svn add
command if you don't want a fully recursive crawl for things
to add.