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/auto_update/src/auto_update.rs

@@ -1,4 +1,4 @@
-use anyhow::{Context as _, Result, anyhow};
+use anyhow::{Context as _, Result};
 use client::{Client, TelemetrySettings};
 use db::RELEASE_CHANNEL;
 use db::kvp::KEY_VALUE_STORE;
@@ -367,7 +367,7 @@ impl AutoUpdater {
             cx.default_global::<GlobalAutoUpdate>()
                 .0
                 .clone()
-                .ok_or_else(|| anyhow!("auto-update not initialized"))
+                .context("auto-update not initialized")
         })??;
 
         let release = Self::get_release(
@@ -411,7 +411,7 @@ impl AutoUpdater {
             cx.default_global::<GlobalAutoUpdate>()
                 .0
                 .clone()
-                .ok_or_else(|| anyhow!("auto-update not initialized"))
+                .context("auto-update not initialized")
         })??;
 
         let release = Self::get_release(
@@ -465,12 +465,11 @@ impl AutoUpdater {
             let mut body = Vec::new();
             response.body_mut().read_to_end(&mut body).await?;
 
-            if !response.status().is_success() {
-                return Err(anyhow!(
-                    "failed to fetch release: {:?}",
-                    String::from_utf8_lossy(&body),
-                ));
-            }
+            anyhow::ensure!(
+                response.status().is_success(),
+                "failed to fetch release: {:?}",
+                String::from_utf8_lossy(&body),
+            );
 
             serde_json::from_slice(body.as_slice()).with_context(|| {
                 format!(
@@ -557,10 +556,10 @@ impl AutoUpdater {
 
         let installer_dir = InstallerDir::new().await?;
         let filename = match OS {
-            "macos" => Ok("Zed.dmg"),
+            "macos" => anyhow::Ok("Zed.dmg"),
             "linux" => Ok("zed.tar.gz"),
             "windows" => Ok("ZedUpdateInstaller.exe"),
-            _ => Err(anyhow!("not supported: {:?}", OS)),
+            unsupported_os => anyhow::bail!("not supported: {unsupported_os}"),
         }?;
 
         #[cfg(not(target_os = "windows"))]
@@ -581,7 +580,7 @@ impl AutoUpdater {
             "macos" => install_release_macos(&installer_dir, downloaded_asset, &cx).await,
             "linux" => install_release_linux(&installer_dir, downloaded_asset, &cx).await,
             "windows" => install_release_windows(downloaded_asset).await,
-            _ => Err(anyhow!("not supported: {:?}", OS)),
+            unsupported_os => anyhow::bail!("not supported: {unsupported_os}"),
         }?;
 
         this.update(&mut cx, |this, cx| {
@@ -640,12 +639,11 @@ async fn download_remote_server_binary(
     let request_body = AsyncBody::from(serde_json::to_string(&update_request_body)?);
 
     let mut response = client.get(&release.url, request_body, true).await?;
-    if !response.status().is_success() {
-        return Err(anyhow!(
-            "failed to download remote server release: {:?}",
-            response.status()
-        ));
-    }
+    anyhow::ensure!(
+        response.status().is_success(),
+        "failed to download remote server release: {:?}",
+        response.status()
+    );
     smol::io::copy(response.body_mut(), &mut temp_file).await?;
     smol::fs::rename(&temp, &target_path).await?;
 
@@ -792,7 +790,7 @@ async fn install_release_macos(
     let running_app_path = cx.update(|cx| cx.app_path())??;
     let running_app_filename = running_app_path
         .file_name()
-        .ok_or_else(|| anyhow!("invalid running app path"))?;
+        .with_context(|| format!("invalid running app path {running_app_path:?}"))?;
 
     let mount_path = temp_dir.path().join("Zed");
     let mut mounted_app_path: OsString = mount_path.join(running_app_filename).into();