The need is particularly acute if you use IDEs and / or application frameworks, as they both tend to have their own quirky way of arranging files, and most of the folders they use or generate should really not be under source control (especially if you are working with a number of co-workers, who may very well use different IDEs, platforms or even OSes).
The process is rather straightforward: you add a couple of lines (possibly preceded by a comment) to .hgignore, usually specifying the folders to avoid using a RegEx.
Having grown tired of typing this up every time, I decided that a simple shell script was in order[*] to save myself some typing (as Martin Fowler said: "I'm a lazy person: I'm prepared to work pretty hard to save myself work").
The only quirk is that there is a minor difference in the RegEx you want, depending on whether you are trying to ignore a directory or a file (possibly a file pattern, such as all .class files, where you would use something like ".*\.class$" for your RegEx).
The script handles this very simplistically, checking whether the passed parameter corresponds to an existing directory, and, if not, treats it as a straightforward pattern that simply gets copied to .hgignore.
I am positive there may well be a number of corner cases where this all fails abysmally; but in that event, it's probably much simpler to directly edit .hgignore, than trying to ferret out the cleverest possible algorithm.
Here it is, in all its glorious banality: I post it here, just in case others may find it useful (if you do, and find yourself improving on it, please feel free to post back comments with your suggestions).
#!/bin/bash[*] I do not even attempt to pretend I know the first thing about shell scripts: however, the above seemed trivial enough that I felt reasonably confident that it should do no harm, despite my n00b-ness.
# Simple script to add a folder to the list of those ignored by hg
# Usage: hgignore FOLDER [COMMENT]
# Created by M. Massenzio (c) 2010 AlertAvert.com
USAGE="Usage: hgignore FOLDER [COMMENT]"
if [ ! -e .hgignore ]; then
echo "Could not find .hgignore in the current directory:"
echo "are you sure this project is being tracked by HG (Mercurial)?"
if [ ! -z "$2" ]; then
echo "# $2" >> .hgignore
if [ -z "$1" ]; then
echo "syntax: regexp" >> .hgignore
if [ -d $1 ]; then
echo "^$1\$" >> .hgignore
echo "Added directory $1 to the list of ignored directories in .hgignore:"
echo "\\$1\$" >> .hgignore
echo "Added file pattern $1 to the list of ignored files in .hgignore:"
echo "" >> .hgignore
echo "--- Contents of .hgignore ---"
echo "--- File ends ---"