h1 {
  background-image: url('header-background.png');
}

.
├── my.css
├── header-background.png → header-background.dVkX3MK.png
└── header-background.dVkX3MK.png

webdeps replace . my.css

h1 {
  background-image: url('header-background.dVkX3MK.png');
}

You can use webdeps list to list dependencies of an asset, which can be useful in build tools. For example:

my.css : css/my.css $(shell webdeps list css/my.css)
	webdeps replace --css . < $< > $@

%.png : image/%.png
	optipng -out $@ $<

Running make my.css will ensure that any assets referenced in my.css are available before running the build commands.

webdeps --help

Webdeps looks for:

• @import statements and url function calls containing literal URLs

• import statements

Webdeps excludes any data: URIs and any URLs with hostnames you haven’t explicitly included.

• Support HTML (i.e. src attribute of img tag, etc.).
• Support arbitrarily nested assets (CSS attributes in JS inside of HTML, etc.).
• Support asset mapping in manifest files (instead of just symlinks in directories).
• Export a PostCSS plugin.