背景：SVN的项目文件被普通用户误删了，这是个非常严重的错误，还好恢复的及时，不然的话，后果不堪设想。但是由于删除的文件比较多，注释的内容简单，恢复的时候需要一个个的保存到本地，然后再上传到服务器上，开发这些模块的小伙伴们还会遇到提交代码版本冲突的问题。由于波及的范围比较大，所以领导让我研究一下，怎么才能禁止普通用户删除SVN中的项目文件。于是，这篇文章就诞生了。
【操作步骤】
1、找到需要加权限的版本库中hooks目录下的pre-commit.tmpl文件，将其重命名，将后缀去掉，为pre-commit脚本文件。如果没有该文件，则新建脚本pre-commit。
每个文件的作用范围：
post-commit
在提交完成，成功创建版本之后执行该钩子，提交已经完成，不可更改，因此本脚本的返回值被忽略。
post-lock
对文件进行加锁操作之后执行该脚本
post-revprop-change
在修改 revision 属性之后，执行该脚本。因为修改稿已经完成，不可更改，因此本脚本的返回值被忽略（不过实际上的实现似乎是该脚本的正确执行与否影响属性修改）
post-unlock
对文件进行解锁操作之后执行该脚本
pre-commit
在 Subversion transaction 完毕之后，在提交之前，执行该脚本
pre-lock
对文件进行加锁操作之前执行该脚本
pre-revprop-change
在修改 revision 属性之前，执行该脚本
pre-unlock
对文件进行解锁操作之前执行该脚本
start-commit
在客户端还没有向服务器提交数据之前，即还没有建立 Subversion transaction（缩写为 txn） 之前，执行执行该脚本
2、修改pre-commit文件内容
原来的内容都注释掉，即在没有“#”的代码前加“#”，然后添加下面的内容：
#!/bin/sh
# PRE-COMMIT HOOK
#
# The pre-commit hook is invoked before a Subversion txn is
# committed. Subversion runs this hook by invoking a program
# (script, executable, binary, etc.) named 'pre-commit' (for which
# this file is a template), with the following ordered arguments:
#
# [1] REPOS-PATH (the path to this repository)
# [2] TXN-NAME (the name of the txn about to be committed)
#
# [STDIN] LOCK-TOKENS ** the lock tokens are passed via STDIN.
#
# If STDIN contains the line "LOCK-TOKENS:\n" (the "\n" denotes a
# single newline), the lines following it are the lock tokens for
# this commit. The end of the list is marked by a line containing
# only a newline character.
#
# Each lock token line consists of a URI-escaped path, followed
# by the separator character '|', followed by the lock token string,
# followed by a newline.
#
# The default working directory for the invocation is undefined, so
# the program should set one explicitly if it cares.
#
# If the hook program exits with success, the txn is committed; but
# if it exits with failure (non-zero), the txn is aborted, no commit
# takes place, and STDERR is returned to the client. The hook
# program can use the 'svnlook' utility to help it examine the txn.
#
# On a Unix system, the normal procedure is to have 'pre-commit'
# invoke other programs to do the real work, though it may do the
# work itself too.
#
# *** NOTE: THE HOOK PROGRAM MUST NOT MODIFY THE TXN, EXCEPT ***
# *** FOR REVISION PROPERTIES (like svn:log or svn:author). ***
#
# This is why we recommend using the read-only 'svnlook' utility.
# In the future, Subversion may enforce the rule that pre-commit
# hooks should not modify the versioned data in txns, or else come
# up with a mechanism to make it safe to do so (by informing the
# committing client of the changes). However, right now neither
# mechanism is implemented, so hook writers just have to be careful.
#
# Note that 'pre-commit' must be executable by the user(s) who will
# invoke it (typically the user httpd runs as), and that user must
# have filesystem-level permission to access the repository.
#
# On a Windows system, you should name the hook program
# 'pre-commit.bat' or 'pre-commit.exe',
# but the basic idea is the same.
#
# The hook program typically does not inherit the environment of
# its parent process. For example, a common problem is for the
# PATH environment variable to not be set to its usual value, so
# that subprograms fail to launch unless invoked via absolute path.
# If you're having unexpected problems with a hook program, the
# culprit may be unusual (or missing) environment variables.
#
# Here is an example hook script, for a Unix /bin/sh interpreter.
# For more examples and pre-written hooks, see those in
# the Subversion repository at
# http://svn.apache.org/repos/asf/subversion/trunk/tools/hook-scripts/ and
# http://svn.apache.org/repos/asf/subversion/trunk/contrib/hook-scripts/
REPOS="$1"
TXN="$2"
# Make sure that the log message contains some text.
SVNLOOK=/usr/bin/svnlook
$SVNLOOK log -t "$TXN" "$REPOS" | \
grep "[a-zA-Z0-9]" > /dev/null || exit 1
# Check that the author of this commit has the rights to perform
# the commit on the files and directories being modified.
commit-access-control.pl "$REPOS" "$TXN" commit-access-control.cfg || exit 1
# All checks passed, so allow the commit.
exit 0
3、给钩子脚本执行权限 chmod 755 pre-commit，不需要重启
Commit blocked by pre-commit hook (exit code 255) with no output.
遇到这个错误解决了半天，对网上的文档也是醉了。注意了SVNLOOK如果不知道的话，使用which svnlook可以查询到。
还有就是头文件缺少#!bin/sh 这个错误真的是无语
也不就是权限不够 可以选择chmod a+x pre-commit 这样授权，保证万无一失。