chore: add delve Go debugger to Guix manifest (#12662)

I did some research and experiments to get a working `delve` debugger using Guix, which could step Forgejo and inspect variables/call procedures. This suggested change captures the details in the Guix manifest to make that knowledge easier for others to reuse.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/12662
Reviewed-by: Mathieu Fenniak <mfenniak@noreply.codeberg.org>

manifest.scm

@@ -11,28 +11,62 @@
 ;;; made available to fetch required Go and Node dependencies.
 ;;;
 #|
+
 guix shell -CNF --share=$HOME -m manifest.scm
 export GOTOOLCHAIN=local     # to use the Go binary from Guix
 export CC=gcc CGO_ENABLED=1
+# The following is to preserve debug info symbols:
+export STRIP=0 CGO_CFLAGS='-O0 -g' EXTRA_GOFLAGS='-gcflags="all=-N -l"'
 export TAGS="timetzdata sqlite sqlite_unlock_notify"
 make clean
 make -j$(nproc)
 make test -j$(nproc)         # run unit tests
 make test-sqlite -j$(nproc)  # run integration tests
 make watch                   # run an instance/rebuild on changes
+
+# For debugging, you can either attach the delve debugger like this:
+dlv attach $(pgrep gitea)
+
+# Or start Forgejo directly with it:
+dlv exec ./gitea
+
 |#
-(specifications->manifest
- (list "bash-minimal"
-       "coreutils"
-       "findutils"
-       "gcc-toolchain"
-       "git"                            ;libpcre support is required
-       "git-lfs"
-       "gnupg"
-       "go"
-       "grep"
-       "make"
-       "node"
-       "nss-certs"
-       "openssh"
-       "sed"))
+
+(use-modules (guix packages)
+             (guix utils))
+
+(define go-1.26                         ;minimal version required by Forgejo
+  (specification->package "go@1.26"))
+
+(define (package-with-go base go)
+  "Return a variant of BASE, a Guix package object built with GO, another
+package."
+  (package/inherit base
+    (arguments (ensure-keyword-arguments (package-arguments base)
+                                         (list #:go go)))))
+
+(define packages-for-debugging
+  (list (specification->package "procps")   ;pgrep
+        (package-with-go (specification->package "delve") go-1.26)     ;debugger
+        (package-with-go (specification->package "gomacro") go-1.26))) ;Go REPL
+
+(concatenate-manifests
+ (list
+  (packages->manifest
+   (append (list go-1.26)
+           packages-for-debugging))
+  (specifications->manifest
+   (list "bash-minimal"
+         "coreutils"
+         "diffutils"
+         "findutils"
+         "gcc-toolchain"
+         "git"                            ;libpcre support is required
+         "git-lfs"
+         "gnupg"
+         "grep"
+         "make"
+         "node"
+         "nss-certs"
+         "openssh"
+         "sed"))))