maps: add the "exists" method to RevMap This is a part of the bigger plan to get rid of reading or writing rev_map directly without going through the RevMap class. Before this patch, there is no easy way to know if the RevMap file exists or not, so the revset functions "fromsvn" and "svnrev" choose to read the rev_map file directly, and throw an exception if the file does not exist. This patch adds the "exists" method that will be used in svnmeta next patch, so these revset functions can test if the file exists without reading the rev_map file directly.

#!/bin/sh
#
# Generate copies.svndump
#

rm -rf temp
mkdir temp
cd temp
mkdir -p import/trunk/dir
echo a > import/trunk/dir/a

svnadmin create testrepo
svnurl=file://`pwd`/testrepo
svn import import $svnurl -m init

svn co $svnurl project
cd project
svn cp trunk/dir trunk/dir2
echo b >> trunk/dir2/a
svn ci -m 'copy/edit trunk/dir/a'
svn up
svn cp trunk/dir2 trunk/dir3
svn ci -m 'copy dir2 to dir3'
svn rm trunk/dir3/a
svn cp trunk/dir2/a trunk/dir3/a
svn ci -m 'copy and remove'
cd ..

svnadmin dump testrepo > ../copies.svndump