doc(Cache): mention arguments to cache lookup help (leanprover-community#21701)

Further, fix docstring refering to `Lean.versionString` even though `Lean.gitHash` is used, and fix a Zulip link.

Author: joneugster

Cache/Hashing.lean

@@ -60,9 +60,9 @@ Computes the root hash, which mixes the hashes of the content of:
 * `lakefile.lean`
 * `lean-toolchain`
 * `lake-manifest.json`
-and the hash of `Lean.versionString`.
+and the hash of `Lean.gitHash`.
 
-(We hash `Lean.versionString` in case the toolchain changes even though `lean-toolchain` hasn't.
+(We hash `Lean.gitHash` in case the toolchain changes even though `lean-toolchain` hasn't.
 This happens with the `lean-pr-testing-NNNN` toolchains when Lean 4 PRs are updated.)
 -/
 def getRootHash : CacheM UInt64 := do

Cache/Main.lean

@@ -11,16 +11,16 @@ Usage: cache [COMMAND]
 
 Commands:
   # No privilege required
-  get  [ARGS]  Download linked files missing on the local cache and decompress
-  get! [ARGS]  Download all linked files and decompress
-  get- [ARGS]  Download linked files missing to the local cache, but do not decompress
-  pack         Compress non-compressed build files into the local cache
-  pack!        Compress build files into the local cache (no skipping)
-  unpack       Decompress linked already downloaded files
-  unpack!      Decompress linked already downloaded files (no skipping)
-  clean        Delete non-linked files
-  clean!       Delete everything on the local cache
-  lookup       Show information about cache files for the given lean files
+  get  [ARGS]   Download linked files missing on the local cache and decompress
+  get! [ARGS]   Download all linked files and decompress
+  get- [ARGS]   Download linked files missing to the local cache, but do not decompress
+  pack          Compress non-compressed build files into the local cache
+  pack!         Compress build files into the local cache (no skipping)
+  unpack        Decompress linked already downloaded files
+  unpack!       Decompress linked already downloaded files (no skipping)
+  clean         Delete non-linked files
+  clean!        Delete everything on the local cache
+  lookup [ARGS] Show information about cache files for the given lean files
 
   # Privilege required
   put          Run 'mk' then upload linked files missing on the server

Cache/Requests.lean

@@ -8,7 +8,7 @@ import Cache.Hashing
 
 namespace Cache.Requests
 
--- FRO cache is flaky so disable until we work out the kinks: https://leanprover.zulipchat.com/#narrow/stream/113488-general/topic/The.20cache.20doesn't.20work/near/411058849
+-- FRO cache is flaky so disable until we work out the kinks: https://leanprover.zulipchat.com/#narrow/channel/113488-general/topic/The.20cache.20doesn't.20work/near/411058849
 def useFROCache : Bool := false
 
 /-- Public URL for mathlib cache -/