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/dap/src/adapters.rs

@@ -1,5 +1,5 @@
 use ::fs::Fs;
-use anyhow::{Context as _, Result, anyhow};
+use anyhow::{Context as _, Result};
 use async_compression::futures::bufread::GzipDecoder;
 use async_tar::Archive;
 use async_trait::async_trait;
@@ -103,8 +103,8 @@ impl TcpArguments {
     pub fn from_proto(proto: proto::TcpHost) -> anyhow::Result<Self> {
         let host = TcpArgumentsTemplate::from_proto(proto)?;
         Ok(TcpArguments {
-            host: host.host.ok_or_else(|| anyhow!("missing host"))?,
-            port: host.port.ok_or_else(|| anyhow!("missing port"))?,
+            host: host.host.context("missing host")?,
+            port: host.port.context("missing port")?,
             timeout: host.timeout,
         })
     }
@@ -200,9 +200,7 @@ impl DebugTaskDefinition {
     }
 
     pub fn from_proto(proto: proto::DebugTaskDefinition) -> Result<Self> {
-        let request = proto
-            .request
-            .ok_or_else(|| anyhow::anyhow!("request is required"))?;
+        let request = proto.request.context("request is required")?;
         Ok(Self {
             label: proto.label.into(),
             initialize_args: proto.initialize_args.map(|v| v.into()),
@@ -346,12 +344,11 @@ pub async fn download_adapter_from_github(
         .get(&github_version.url, Default::default(), true)
         .await
         .context("Error downloading release")?;
-    if !response.status().is_success() {
-        Err(anyhow!(
-            "download failed with status {}",
-            response.status().to_string()
-        ))?;
-    }
+    anyhow::ensure!(
+        response.status().is_success(),
+        "download failed with status {}",
+        response.status().to_string()
+    );
 
     match file_type {
         DownloadedFileType::GzipTar => {