Make cargo feature additive

.azure-pipelines.yml

@@ -61,5 +61,6 @@ stages:
               rmdir /Q /S target\.rustc_info.json
               rmdir /Q /S target\debug\examples
               rmdir /Q /S target\debug\incremental
+              rmdir /Q /S target\tests\target\debug\incremental
             displayName: Cleaning for cache
             continueOnError: true

.travis.yml

@@ -35,6 +35,7 @@ jobs:
     - {}
     - rust: beta
     - rust: nightly
+      cache: false
     - name: Linting (fmt + clippy)
       before_script:
         - rustup component add clippy

Cargo.toml

@@ -81,14 +81,14 @@ version-sync = "0.8"
 criterion = "0.3"
 
 [features]
-default     = ["suggestions", "color", "vec_map", "derive", "std"]
+default     = ["suggestions", "color", "vec_map", "derive", "std", "cargo"]
 std         = [] # support for no_std in a backwards-compatible way
 suggestions = ["strsim"]
 color       = ["ansi_term", "atty"]
 wrap_help   = ["term_size", "textwrap/term_size"]
 derive      = ["clap_derive", "lazy_static"]
 yaml        = ["yaml-rust"]
-no_cargo    = [] # Enable if you're not using Cargo, disables Cargo-env-var-dependent macros
+cargo       = [] # Disable if you're not using Cargo, enables Cargo-env-var-dependent macros
 unstable    = [] # for building with unstable clap features (doesn't require nightly Rust) (currently none)
 nightly     = [] # for building with unstable Rust features (currently none)
 debug       = [] # Enables debug messages

src/macros.rs

@@ -426,7 +426,7 @@ macro_rules! arg_enum {
 ///             .get_matches();
 /// # }
 /// ```
-#[cfg(not(feature = "no_cargo"))]
+#[cfg(feature = "cargo")]
 #[macro_export]
 macro_rules! crate_version {
     () => {
@@ -455,7 +455,7 @@ macro_rules! crate_version {
 ///             .get_matches();
 /// # }
 /// ```
-#[cfg(not(feature = "no_cargo"))]
+#[cfg(feature = "cargo")]
 #[macro_export]
 macro_rules! crate_authors {
     ($sep:expr) => {{
@@ -515,7 +515,7 @@ macro_rules! crate_authors {
 ///             .get_matches();
 /// # }
 /// ```
-#[cfg(not(feature = "no_cargo"))]
+#[cfg(feature = "cargo")]
 #[macro_export]
 macro_rules! crate_description {
     () => {
@@ -536,7 +536,7 @@ macro_rules! crate_description {
 ///             .get_matches();
 /// # }
 /// ```
-#[cfg(not(feature = "no_cargo"))]
+#[cfg(feature = "cargo")]
 #[macro_export]
 macro_rules! crate_name {
     () => {
@@ -567,7 +567,7 @@ macro_rules! crate_name {
 /// let m = app_from_crate!().get_matches();
 /// # }
 /// ```
-#[cfg(not(feature = "no_cargo"))]
+#[cfg(feature = "cargo")]
 #[macro_export]
 macro_rules! app_from_crate {
     () => {