feat: add minimal support for Debian pre-dependencies (#696)

* feat: add minimal support for Debian pre-dependencies

Basic support for adding 'Pre-Depends:' to Debian packages added.

* Make Predefined a debian-specific modification

Based on feedback from @caarlos0.

* Add some coverage of pre-depend Debian field in unit tests

* Update the configuration example to include Debian-specific predepends reference

deb/deb.go

@@ -720,6 +720,9 @@ Replaces: {{join .}}
 {{- with nonEmpty .Info.Provides}}
 Provides: {{join .}}
 {{- end }}
+{{- with .Info.Deb.Predepends}}
+Pre-Depends: {{join .}}
+{{- end }}
 {{- with .Info.Depends}}
 Depends: {{join .}}
 {{- end }}

deb/deb_test.go

@@ -88,6 +88,9 @@ func exampleInfo() *nfpm.Info {
 					Type:        files.TypeDir,
 				},
 			},
+			Deb: nfpm.Deb{
+				Predepends: []string{"less"},
+			},
 		},
 	})
 }

deb/testdata/bad_provides.golden

@@ -6,6 +6,7 @@ Architecture: amd64
 Maintainer: Carlos A Becker <[email protected]>
 Installed-Size: 0
 Replaces: svn
+Pre-Depends: less
 Depends: bash
 Recommends: git
 Suggests: bash

deb/testdata/control.golden

@@ -7,6 +7,7 @@ Maintainer: Carlos A Becker <[email protected]>
 Installed-Size: 10
 Replaces: svn
 Provides: bzr
+Pre-Depends: less
 Depends: bash
 Recommends: git
 Suggests: bash

nfpm.go

@@ -235,6 +235,7 @@ func (c *Config) expandEnvVars() {
 	for k, v := range c.Info.Deb.Fields {
 		c.Info.Deb.Fields[k] = os.Expand(v, c.envMappingFunc)
 	}
+	c.Info.Deb.Predepends = c.expandEnvVarsStringSlice(c.Info.Deb.Predepends)
 }
 
 // Info contains information about a single package.
@@ -390,6 +391,7 @@ type Deb struct {
 	Signature   DebSignature      `yaml:"signature,omitempty" json:"signature,omitempty" jsonschema:"title=signature"`
 	Compression string            `yaml:"compression,omitempty" json:"compression,omitempty" jsonschema:"title=compression algorithm to be used,enum=gzip,enum=xz,enum=none,default=gzip"`
 	Fields      map[string]string `yaml:"fields,omitempty" json:"fields,omitempty" jsonschema:"title=fields"`
+	Predepends  []string          `yaml:"predepends,omitempty" json:"predepends,omitempty" jsonschema:"title=predepends directive,example=nfpm"`
 }
 
 type DebSignature struct {

www/docs/configuration.md

@@ -408,6 +408,12 @@ deb:
   fields:
     Bugs: https://github.com/goreleaser/nfpm/issues
 
+  # The Debian-specific "predepends" field can be used to ensure the complete installation of a list of
+  # packages (including unpacking, pre- and post installation scripts) prior to the installation of the
+  # built package.
+  predepends:
+    - baz (>= 1.2.3-0)
+
 apk:
   # apk specific architecture name that overrides "arch" without performing any replacements.
   apk_arch: armhf