As we described in 第 2.2 节 “修订版本”, revision numbers in Subversion are pretty straightforward—integers that keep getting larger as you commit more changes to your versioned data. Still, it doesn't take long before you can no longer remember exactly what happened in each and every revision. Fortunately, the typical Subversion workflow doesn't often demand that you supply arbitrary revisions to the Subversion operations you perform. For operations that do require a revision specifier, you generally supply a revision number that you saw in a commit email, in the output of some other Subversion operation, or in some other context that would give meaning to that particular number.
![[注意]](images/note.png)
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注意 |
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Referring to revision numbers with an “ |
But occasionally, you need to pinpoint a moment in time for which you don't already have a revision number memorized or handy. So besides the integer revision numbers, svn allows as input some additional forms of revision specifiers: revision keywords and revision dates.
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The various forms of Subversion revision specifiers can be mixed and matched
when used to specify revision ranges. For example, you can use |
The Subversion client understands a number of revision keywords. These
keywords can be used instead of integer arguments to the
--revision (-r) option, and are resolved
into specific revision numbers by Subversion:
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HEAD -
版本库中最新的(或者是“最年轻的”)版本。
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BASE -
The revision number of an item in a working copy. If the item has been locally modified, this refers to the way the item appears without those local modifications.
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COMMITTED -
项目最近修改的修订版本，与
BASE相同或更早。 -
PREV -
The revision immediately before the last revision in which an item changed. Technically, this boils down to
COMMITTED-1.
As can be derived from their descriptions, the PREV,
BASE, and COMMITTED revision keywords
are used only when referring to a working copy path—they don't apply
to repository URLs. HEAD, on the other hand, can be used
in conjunction with both of these path types.
下面是一些修订版本关键字的例子：
$ svn diff -r PREV:COMMITTED foo.c # shows the last change committed to foo.c $ svn log -r HEAD # shows log message for the latest repository commit $ svn diff -r HEAD # compares your working copy (with all of its local changes) to the # latest version of that tree in the repository $ svn diff -r BASE:HEAD foo.c # compares the unmodified version of foo.c with the latest version of # foo.c in the repository $ svn log -r BASE:HEAD # shows all commit logs for the current versioned directory since you # last updated $ svn update -r PREV foo.c # rewinds the last change on foo.c, decreasing foo.c's working revision $ svn diff -r BASE:14 foo.c # compares the unmodified version of foo.c with the way foo.c looked # in revision 14
Revision numbers reveal nothing about the world outside the version control
system, but sometimes you need to correlate a moment in real time with a
moment in version history. To facilitate this, the
--revision (-r) option can also accept as
input date specifiers wrapped in curly braces ({ and
}). Subversion accepts the standard ISO-8601 date and
time formats, plus a few others. Here are some examples.
$ svn checkout -r {2006-02-17}
$ svn checkout -r {15:30}
$ svn checkout -r {15:30:00.200000}
$ svn checkout -r {"2006-02-17 15:30"}
$ svn checkout -r {"2006-02-17 15:30 +0230"}
$ svn checkout -r {2006-02-17T15:30}
$ svn checkout -r {2006-02-17T15:30Z}
$ svn checkout -r {2006-02-17T15:30-04:00}
$ svn checkout -r {20060217T1530}
$ svn checkout -r {20060217T1530Z}
$ svn checkout -r {20060217T1530-0500}
…
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Keep in mind that most shells will require you to, at a minimum, quote or otherwise escape any spaces that are included as part of revision date specifiers. Certain shells may also take issue with the unescaped use of curly brances, too. Consult your shell's documentation for the requirements specific to your environment. |
当你指定一个日期，Subversion会在版本库找到接近这个日期的最近版本，并且对这个版本继续操作：
$ svn log -r {2006-11-28}
------------------------------------------------------------------------
r12 | ira | 2006-11-27 12:31:51 -0600 (Mon, 27 Nov 2006) | 6 lines
…
你可以使用时间段。Subversion 会找到这段时间的所有版本：
$ svn log -r {2006-11-20}:{2006-11-29}
…
![[警告]](images/warning.png)
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Since the timestamp of a revision is stored as an unversioned, modifiable property of the revision (see 第 3 节 “属性”), revision timestamps can be changed to represent complete falsifications of true chronology, or even removed altogether. Subversion's ability to correctly convert revision dates into real revision numbers depends on revision datestamps maintaining a sequential ordering—the younger the revision, the younger its timestamp. If this ordering isn't maintained, you will likely find that trying to use dates to specify revision ranges in your repository doesn't always return the data you might have expected. |