direnv version <version_at_least>

Add a stdlib function to check that direnv is at least as old as the
desired version.

cmd_version.go

@@ -2,15 +2,34 @@ package main
 
 import (
 	"fmt"
+	"strings"
+
+	"golang.org/x/mod/semver"
 )
 
 // CmdVersion is `direnv version`
 var CmdVersion = &Cmd{
 	Name:    "version",
-	Desc:    "prints the version (" + Version + ")",
+	Desc:    "prints the version (" + Version + ") or checks that direnv is older than VERSION_AT_LEAST.",
+	Args:    []string{"[VERSION_AT_LEAST]"},
 	Aliases: []string{"--version"},
 	Action: actionSimple(func(env Env, args []string) error {
-		fmt.Println(Version)
+		semVersion := "v" + Version
+		if len(args) > 1 {
+			atLeast := args[1]
+			if !strings.HasPrefix(atLeast, "v") {
+				atLeast = "v" + atLeast
+			}
+			if !semver.IsValid(atLeast) {
+				return fmt.Errorf("%s is not a valid semver version", atLeast)
+			}
+			cmp := semver.Compare(semVersion, atLeast)
+			if cmp < 0 {
+				return fmt.Errorf("%s it older than the desired %s", semVersion, atLeast)
+			}
+		} else {
+			fmt.Println(Version)
+		}
 		return nil
 	}),
 }

go.mod

@@ -5,4 +5,5 @@ go 1.12
 require (
 	github.com/BurntSushi/toml v0.3.1
 	github.com/direnv/go-dotenv v0.0.0-20181227095604-4cce6d1a66f7
+	golang.org/x/mod v0.2.0
 )

go.sum

@@ -2,3 +2,16 @@ github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/direnv/go-dotenv v0.0.0-20181227095604-4cce6d1a66f7 h1:JsyIu/zmj8ZuCbyTRYczeOaxLsnSDCAmRwHa0jl4YqY=
 github.com/direnv/go-dotenv v0.0.0-20181227095604-4cce6d1a66f7/go.mod h1:T/OO6ZHPlA9WCvpwKhgyBiWiMcLwbP/rsGgxkxVHk6g=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
+golang.org/x/mod v0.2.0 h1:KU7oHjnv3XNWfa5COkzUifxZmxp1TyI7ImMXqFxLwvQ=
+golang.org/x/mod v0.2.0/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

man/direnv-stdlib.1.md

@@ -229,6 +229,12 @@ Example (.envrc):
 
     watch_file Gemfile
 
+### `direnv_version <version_at_least>`
+
+Checks that the direnv version is at least old as `version_at_least`. This can
+be useful when sharing an `.envrc` and to make sure that the users are up to
+date.
+
 COPYRIGHT
 ---------
 

stdlib.go

@@ -797,6 +797,13 @@ const StdLib = "#!/usr/bin/env bash\n" +
 	"  eval \"$(guix environment \"$@\" --search-paths)\"\n" +
 	"}\n" +
 	"\n" +
+	"# Usage: direnv_version <version_at_least>\n" +
+	"#\n" +
+	"# Checks that the direnv version is at least old as <version_at_least>.\n" +
+	"direnv_version() {\n" +
+	"  \"$direnv\" version \"$@\"\n" +
+	"}\n" +
+	"\n" +
 	"# Usage: __main__ <cmd> [...<args>]\n" +
 	"#\n" +
 	"# Used by rc.go\n" +

stdlib.sh

@@ -794,6 +794,13 @@ use_guix() {
   eval "$(guix environment "$@" --search-paths)"
 }
 
+# Usage: direnv_version <version_at_least>
+#
+# Checks that the direnv version is at least old as <version_at_least>.
+direnv_version() {
+  "$direnv" version "$@"
+}
+
 # Usage: __main__ <cmd> [...<args>]
 #
 # Used by rc.go