diff --git a/nix/overlays/checked-shell-script/checked-shell-script.nix b/nix/overlays/checked-shell-script/checked-shell-script.nix
index 5deb12749c9..942659d6f76 100644
--- a/nix/overlays/checked-shell-script/checked-shell-script.nix
+++ b/nix/overlays/checked-shell-script/checked-shell-script.nix
@@ -13,18 +13,17 @@
 { name
 , docs
 , args ? [ ]
-, addCommandCompletion ? false
+, positionalCompletion ? ""
 , inRootDir ? false
 , redirectTixFiles ? true
 , withEnv ? null
 , withTmpDir ? false
 }: text:
 let
+  # square brackets are a pain to escape - if even possible. just don't use them...
+  escape = str: builtins.replaceStrings [ "\n" ] [ " \\n" ] str;
+
   argsTemplate =
-    let
-      # square brackets are a pain to escape - if even possible. just don't use them...
-      escapedDocs = builtins.replaceStrings [ "\n" ] [ " \\n" ] docs;
-    in
     writeTextFile {
       inherit name;
       destination = "/${name}.m4"; # destination is needed to have the proper basename for completion
@@ -35,7 +34,7 @@ let
           # stripping the /nix/store/... path for nicer display
           BASH_ARGV0="$(basename "$0")"
 
-          # ARG_HELP([${name}], [${escapedDocs}])
+          # ARG_HELP([${name}], [${escape docs}])
           ${lib.strings.concatMapStrings (arg: "# " + arg) args}
           # ARG_POSITIONAL_DOUBLEDASH()
           # ARG_DEFAULTS_POS()
@@ -63,8 +62,8 @@ let
         ${argbash}/bin/argbash --type completion --strip all ${argsTemplate}/${name}.m4 > $out
       ''
 
-      + lib.optionalString addCommandCompletion ''
-        sed 's/COMPREPLY.*compgen -o bashdefault .*$/_command/' -i $out
+      + lib.optionalString (positionalCompletion != "") ''
+        sed 's#COMPREPLY.*compgen -o bashdefault .*$#${escape positionalCompletion}#' -i $out
       ''
     );
 
diff --git a/nix/tools/devtools.nix b/nix/tools/devtools.nix
index 0d480d2c736..f5afe0e1634 100644
--- a/nix/tools/devtools.nix
+++ b/nix/tools/devtools.nix
@@ -28,7 +28,7 @@ let
             "ARG_POSITIONAL_SINGLE([command], [Command to run])"
             "ARG_LEFTOVERS([command arguments])"
           ];
-        addCommandCompletion = true;
+        positionalCompletion = "_command";
         redirectTixFiles = false; # will be done by sub-command
         inRootDir = true;
       }
diff --git a/nix/tools/loadtest.nix b/nix/tools/loadtest.nix
index dcacfa9abca..7c52c653667 100644
--- a/nix/tools/loadtest.nix
+++ b/nix/tools/loadtest.nix
@@ -55,9 +55,12 @@ let
       '';
 
   loadtestAgainst =
+    let
+      name = "postgrest-loadtest-against";
+    in
     checkedShellScript
       {
-        name = "postgrest-loadtest-against";
+        inherit name;
         docs =
           ''
             Run the vegeta loadtest twice:
@@ -68,6 +71,12 @@ let
           "ARG_POSITIONAL_SINGLE([target], [Commit-ish reference to compare with])"
           "ARG_LEFTOVERS([additional vegeta arguments])"
         ];
+        positionalCompletion =
+          ''
+            if test "$prev" == "${name}"; then
+              __gitcomp_nl "$(__git_refs)"
+            fi
+          '';
         inRootDir = true;
       }
       ''
diff --git a/nix/tools/withtools.nix b/nix/tools/withtools.nix
index 0aab76d9f43..bc1e28be1c6 100644
--- a/nix/tools/withtools.nix
+++ b/nix/tools/withtools.nix
@@ -27,7 +27,7 @@ let
             "ARG_USE_ENV([PGRST_DB_SCHEMAS], [test], [Schema to expose])"
             "ARG_USE_ENV([PGRST_DB_ANON_ROLE], [postgrest_test_anonymous], [Anonymous PG role])"
           ];
-        addCommandCompletion = true;
+        positionalCompletion = "_command";
         inRootDir = true;
         redirectTixFiles = false;
         withTmpDir = true;
@@ -121,7 +121,7 @@ let
             "ARG_POSITIONAL_SINGLE([command], [Command to run])"
             "ARG_LEFTOVERS([command arguments])"
           ];
-        addCommandCompletion = true;
+        positionalCompletion = "_command";
         inRootDir = true;
       }
       (lib.concatStringsSep "\n\n" runners);
@@ -130,9 +130,12 @@ let
   withVersions = builtins.map withTmpDb postgresqlVersions;
 
   withGit =
+    let
+      name = "postgrest-with-git";
+    in
     checkedShellScript
       {
-        name = "postgrest-with-git";
+        inherit name;
         docs =
           ''
             Create a new worktree of the postgrest repo in a temporary directory and
@@ -144,7 +147,14 @@ let
             "ARG_POSITIONAL_SINGLE([command], [Command to run])"
             "ARG_LEFTOVERS([command arguments])"
           ];
-        addCommandCompletion = true; # TODO: first positional argument needs git commit completion
+        positionalCompletion =
+          ''
+            if test "$prev" == "${name}"; then
+              __gitcomp_nl "$(__git_refs)"
+            else
+              _command_offset 2
+            fi
+          '';
         inRootDir = true;
       }
       ''
@@ -206,7 +216,7 @@ let
             "ARG_POSITIONAL_SINGLE([command], [Command to run])"
             "ARG_LEFTOVERS([command arguments])"
           ];
-        addCommandCompletion = true;
+        positionalCompletion = "_command";
         inRootDir = true;
         withEnv = postgrest.env;
         withTmpDir = true;
diff --git a/shell.nix b/shell.nix
index bcd96002f6c..cdf760c2116 100644
--- a/shell.nix
+++ b/shell.nix
@@ -43,6 +43,7 @@ lib.overrideDerivation postgrest.env (
       base.buildInputs ++ [
         pkgs.cabal-install
         pkgs.cabal2nix
+        pkgs.git
         pkgs.postgresql
         postgrest.hsie.bin
       ]
@@ -51,6 +52,7 @@ lib.overrideDerivation postgrest.env (
     shellHook =
       ''
         source ${pkgs.bashCompletion}/etc/profile.d/bash_completion.sh
+        source ${pkgs.git}/share/git/contrib/completion/git-completion.bash
         source ${postgrest.hsie.bashCompletion}
 
       ''