Initial

.gitignore

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+/target
+### JetBrains template
+# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion, Android Studio, WebStorm and Rider
+# Reference: https://intellij-support.jetbrains.com/hc/en-us/articles/206544839
+
+# User-specific stuff
+.idea/**/workspace.xml
+.idea/**/tasks.xml
+.idea/**/usage.statistics.xml
+.idea/**/dictionaries
+.idea/**/shelf
+
+# AWS User-specific
+.idea/**/aws.xml
+
+# Generated files
+.idea/**/contentModel.xml
+
+# Sensitive or high-churn files
+.idea/**/dataSources/
+.idea/**/dataSources.ids
+.idea/**/dataSources.local.xml
+.idea/**/sqlDataSources.xml
+.idea/**/dynamic.xml
+.idea/**/uiDesigner.xml
+.idea/**/dbnavigator.xml
+
+# Gradle
+.idea/**/gradle.xml
+.idea/**/libraries
+
+# CMake
+cmake-build-*/
+
+# Mongo Explorer plugin
+.idea/**/mongoSettings.xml
+
+# File-based project format
+*.iws
+
+# mpeltonen/sbt-idea plugin
+.idea_modules/
+
+# Cursive Clojure plugin
+.idea/replstate.xml
+
+# SonarLint plugin
+.idea/sonarlint/
+
+# Crashlytics plugin (for Android Studio and IntelliJ)
+com_crashlytics_export_strings.xml
+crashlytics.properties
+crashlytics-build.properties
+fabric.properties
+
+# Editor-based Rest Client
+.idea/httpRequests
+
+# Android studio 3.1+ serialized cache file
+.idea/caches/build_file_checksums.ser
+
+### Rust template
+# Generated by Cargo
+# will have compiled files and executables
+debug/
+target/
+
+# These are backup files generated by rustfmt
+**/*.rs.bk
+
+# MSVC Windows builds of rustc generate these, which store debugging information
+*.pdb
+
+
+
+# Added by cargo
+#
+# already existing elements were commented out
+
+#/target
+/Cargo.lock

.idea/.gitignore

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+# Default ignored files
+/shelf/
+/workspace.xml
+# Editor-based HTTP Client requests
+/httpRequests/
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml

.idea/envhead.iml

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+<?xml version="1.0" encoding="UTF-8"?>
+<module type="EMPTY_MODULE" version="4">
+  <component name="NewModuleRootManager">
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
+      <excludeFolder url="file://$MODULE_DIR$/target" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+  </component>
+</module>

.idea/modules.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectModuleManager">
+    <modules>
+      <module fileurl="file://$PROJECT_DIR$/.idea/envhead.iml" filepath="$PROJECT_DIR$/.idea/envhead.iml" />
+    </modules>
+  </component>
+</project>

.idea/vcs.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="" vcs="Git" />
+  </component>
+</project>

Cargo.toml

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+[package]
+name = "envhead"
+version = "1.0.0"
+edition = "2021"
+authors = ["Thorsten Sommer"]
+description = "A crate to build environment variable names using a static prefix. Works great with the popular clap crate."
+license = "MIT"
+homepage = "https://devops.tsommer.org/open-source/rust/crates/envhead"
+repository = "https://devops.tsommer.org/open-source/rust/crates/envhead"
+readme = "README.md"
+keywords = ["cli", "shell", "clap", "os"]
+categories = ["command-line-interface", "development-tools::procedural-macro-helpers"]
+
+[lib]
+proc-macro = true
+
+[dependencies]
+quote = "1.0.33"
+syn = "2.0.39"

LICENSE

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+Copyright (c) 2023 Thorsten Sommer
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# Envhead
+
+Envhead is a crate that creates environment variable names using a static prefix. The desired prefix is defined in your build script `build.rs`.
+
+### Usage
+
+First, you should define the prefix in your `build.rs` file. In this example, we will use `MY_APP` as the prefix:
+
+```rust
+fn main() {
+    println!("cargo:rustc-env=ENV_HEAD_PREFIX=MY_APP");
+}
+```
+
+When the `ENV_HEAD_PREFIX` variable is not defined, `ENV` is used as the default prefix.
+
+Then, in your code, you can use the `envhead!` macro to create environment variable names.
+
+```rust
+use envhead::envhead;
+
+fn main() {
+    let env_var = envhead!("server_port");
+
+    // Prints "MY_APP_SERVER_PORT":
+    println!("{}", env_var);
+}
+```
+
+You might find it useful to use `envhead` together with `clap` to create environment variable names for your command line arguments:
+
+```rust
+use clap::Args;
+use envhead::envhead;
+
+#[derive(Debug, Args)]
+pub struct ServerArgs {
+    #[arg(
+        short = 'p', long,
+        required = false,
+        value_name = "port",
+        value_hint = clap::ValueHint::Other,
+        help = "The server's port.",
+        default_value_t = 8000,
+        env = envhead!("server_port"),
+    )]
+    pub port: u16,
+
+    #[arg(
+        long,
+        required = true,
+        value_name = "SECRET_TOKEN",
+        value_hint = clap::ValueHint::Other,
+        help = "The secret token to authenticate the client.",
+        env = envhead!("server_secret_token"),
+    )]
+    pub secret_token: Option<String>,
+}
+```
+
+# Changelog
+
+### Version 1.0.0
+- Initial release

src/lib.rs

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+extern crate proc_macro;
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{parse_macro_input, LitStr};
+
+/// This macro is used to get the environment variable prefixed with the `ENV_LEAD_PREFIX` environment variable.
+/// If `ENV_LEAD_PREFIX` is not set, it will default to `ENV`. The given string will be converted to uppercase.
+#[proc_macro]
+pub fn envhead(input: TokenStream) -> TokenStream {
+    let prefix = option_env!("ENV_HEAD_PREFIX").unwrap_or("ENV");
+    let input = parse_macro_input!(input as LitStr);
+    let value = input.value();
+    let upper_value = format!("{}_{}", prefix.to_uppercase(), value.to_uppercase());
+    let expanded = quote! {
+        #upper_value
+    };
+
+    TokenStream::from(expanded)
+}