cargo: add clap_mangen

Cargo.lock

@@ -205,6 +205,16 @@ dependencies = [
  "clap 3.1.2",
 ]
 
+[[package]]
+name = "clap_mangen"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0649fb4156bbd7306896025005596033879a2051f9a3aa7416ab915df1f8fdac"
+dependencies = [
+ "clap 3.1.2",
+ "roff",
+]
+
 [[package]]
 name = "config"
 version = "0.11.0"
@@ -571,6 +581,7 @@ dependencies = [
  "chrono",
  "clap 3.1.2",
  "clap_complete",
+ "clap_mangen",
  "config",
  "criterion",
  "criterion_bencher_compat",
@@ -1070,6 +1081,12 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "roff"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b833d8d034ea094b1ea68aa6d5c740e0d04bad9d16568d08ba6f76823a114316"
+
 [[package]]
 name = "rust-ini"
 version = "0.13.0"

Cargo.toml

@@ -28,6 +28,7 @@ atty = "0.2.14"
 chrono = "0.4.19"
 clap = { version = "3.1.0", features = ["cargo"] }
 clap_complete = "3.1.0"
+clap_mangen = "0.1"
 config = "0.11.0"
 criterion = "0.3.5"
 git2 = "0.13.25"