append() does not respect current content if line contains '<'

[ecksun]

I noticed that if I run append() several times with the same content it also appends that line several times, instead of just one time. That is, append() is not idempotent.

If text is already found in filename, the append is not run, and None is returned immediately.

The following small test script can reproduce the issue:

from fabric.contrib.files import append

def run():
      append('testfile', 'some < pipe')

This issue seems to be similar to #341

The error has to do with the '<' symbol.

The problem seems to boil down to the regex that is sent to egrep in contains():
https://github.com/fabric/fabric/blob/master/fabric/contrib/files.py#L360

printing egrep_cmd gives me the following for the above testcase:

egrep "^some\ \<\ pipe$" "$(echo testfile)"

However the correct regex would be:

egrep "^some\ <\ pipe$" "$(echo testfile)"

The incorrect regex seems to be generated by the _escape_for_regex function.

[AndreCimander]

+1, still encountering this bug in 1.12, our poor servers are restoring their iptables rules way too many times x)

[hyperknot]

I believe I've encountered the same one, with > this time.

This adds multiple lines:

append('/etc/rc.local', 'echo never > /sys/kernel/mm/transparent_hugepage/enabled')

[ecksun]

I have provided the fix in the initial description, you can probably create a patch from that and submit it. I'm no longer using fabric so will likely not fix this myself :(

[bitprophet]

Fixed in #1559!