Use anyhow more idiomatically (#31052)

https://github.com/zed-industries/zed/issues/30972 brought up another
case where our context is not enough to track the actual source of the
issue: we get a general top-level error without inner error.

The reason for this was `.ok_or_else(|| anyhow!("failed to read HEAD
SHA"))?; ` on the top level.

The PR finally reworks the way we use anyhow to reduce such issues (or
at least make it simpler to bubble them up later in a fix).
On top of that, uses a few more anyhow methods for better readability.

* `.ok_or_else(|| anyhow!("..."))`, `map_err` and other similar error
conversion/option reporting cases are replaced with `context` and
`with_context` calls
* in addition to that, various `anyhow!("failed to do ...")` are
stripped with `.context("Doing ...")` messages instead to remove the
parasitic `failed to` text
* `anyhow::ensure!` is used instead of `if ... { return Err(...); }`
calls
* `anyhow::bail!` is used instead of `return Err(anyhow!(...));`

Release Notes:

- N/A

crates/languages/src/go.rs

@@ -1,4 +1,4 @@
-use anyhow::{Context as _, Result, anyhow};
+use anyhow::{Context as _, Result};
 use async_trait::async_trait;
 use collections::HashMap;
 use futures::StreamExt;
@@ -107,7 +107,7 @@ impl super::LspAdapter for GoLspAdapter {
                         delegate.show_notification(NOTIFICATION_MESSAGE, cx);
                     })?
                 }
-                return Err(anyhow!("cannot install gopls"));
+                anyhow::bail!("cannot install gopls");
             }
             Ok(())
         }))
@@ -167,10 +167,9 @@ impl super::LspAdapter for GoLspAdapter {
                 String::from_utf8_lossy(&install_output.stdout),
                 String::from_utf8_lossy(&install_output.stderr)
             );
-
-            return Err(anyhow!(
+            anyhow::bail!(
                 "failed to install gopls with `go install`. Is `go` installed and in the PATH? Check logs for more information."
-            ));
+            );
         }
 
         let installed_binary_path = gobin_dir.join(BINARY);
@@ -405,15 +404,12 @@ async fn get_cached_server_binary(container_dir: PathBuf) -> Option<LanguageServ
             }
         }
 
-        if let Some(path) = last_binary_path {
-            Ok(LanguageServerBinary {
-                path,
-                arguments: server_binary_arguments(),
-                env: None,
-            })
-        } else {
-            Err(anyhow!("no cached binary"))
-        }
+        let path = last_binary_path.context("no cached binary")?;
+        anyhow::Ok(LanguageServerBinary {
+            path,
+            arguments: server_binary_arguments(),
+            env: None,
+        })
     })
     .await
     .log_err()