Replace deprecated error_chain crate with anyhow (dandavison#1405)

The `error_chain` crate is now deprecated for a long time and `anyhow`
has proven to be a popular replacement for applications.

This also improves the current error messages for panics.

```
PAGER='"less' git show
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: \
Error(Msg("Could not parse pager command."), State { next_error: Some(ParseError), \
backtrace: InternalBacktrace })', src/main.rs:136:88
```

```
PAGER='"less' git show
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Could not parse pager command.

Caused by:
    missing closing quote', src/main.rs:125:88
```

Cargo.toml

@@ -20,6 +20,7 @@ chrono = "0.4.23"
 chrono-humanize = "0.2.2"
 ansi_colours = "1.2.1"
 ansi_term = "0.12.1"
+anyhow = "1.0.70"
 atty = "0.2.14"
 bitflags = "2.2.1"
 box_drawing = "0.1.2"
@@ -55,10 +56,5 @@ version = "0.28.2"
 default-features = false
 features = []
 
-[dependencies.error-chain]
-version = "0.12.4"
-default-features = false
-features = []
-
 [profile.test]
 opt-level = 2

src/git_config/remote.rs

@@ -129,7 +129,7 @@ impl FromStr for GitRemoteRepo {
                 ),
             })
         } else {
-            Err("Not a GitHub, GitLab, SourceHut or Codeberg repo.".into())
+            Err(anyhow!("Not a GitHub, GitLab, SourceHut or Codeberg repo."))
         }
     }
 }

src/main.rs

@@ -49,13 +49,7 @@ where
 }
 
 pub mod errors {
-    error_chain::error_chain! {
-        foreign_links {
-            Io(::std::io::Error);
-            SyntectError(::syntect::LoadingError);
-            ParseIntError(::std::num::ParseIntError);
-        }
-    }
+    pub use anyhow::{anyhow, Context, Error, Result};
 }
 
 #[cfg(not(tarpaulin_include))]

src/utils/bat/output.rs

@@ -74,8 +74,7 @@ impl OutputType {
             .or(pager_from_env)
             .unwrap_or_else(|| String::from("less"));
 
-        let pagerflags =
-            shell_words::split(&pager).chain_err(|| "Could not parse pager command.")?;
+        let pagerflags = shell_words::split(&pager).context("Could not parse pager command.")?;
 
         Ok(match pagerflags.split_first() {
             Some((pager_name, args)) => {
@@ -117,7 +116,7 @@ impl OutputType {
             OutputType::Pager(ref mut command) => command
                 .stdin
                 .as_mut()
-                .chain_err(|| "Could not open stdin for pager")?,
+                .context("Could not open stdin for pager")?,
             OutputType::Stdout(ref mut handle) => handle,
         })
     }