Wait for git credential helper task (#49980)

This is just something I noticed when reading the code (doesn't fix any
user-facing bug that I'm aware of). It seems that [1] changed wait(t) to
wait(p), which might be a typo? Without wait(t), any error thrown by t
will be ignored.

I've folded wait(p) into the do expression, although the helper should
already be dead by the time read! returns (unless it closes stdout early
for some reason).

[1]
7577ec2

stdlib/LibGit2/src/gitcredential.jl

@@ -183,16 +183,16 @@ end
 
 function run!(helper::GitCredentialHelper, operation::AbstractString, cred::GitCredential)
  cmd = `$(helper.cmd) $operation`
- p = open(cmd, "r+")
-
- # Provide the helper with the credential information we know
- write(p, cred)
- write(p, "\n")
- t = @async close(p.in)
-
- # Process the response from the helper
- Base.read!(p, cred)
- wait(p)
+ open(cmd, "r+") do p
+ # Provide the helper with the credential information we know
+  write(p, cred)
+  write(p, "\n")
+  t = @async close(p.in)
+
+ # Process the response from the helper
+  Base.read!(p, cred)
+  wait(t)
+ end
 
  return cred
 end