store: centralize Fruix path naming

docs/GUIX_DIFFERENCES.md

@@ -197,6 +197,51 @@ So if you come from Guix, assume that Fruix now has:
 - explicit generation metadata roots
 - a real but still modest installed-system switch/rollback UX
 
+## 7. Fruix keeps Guix-like store semantics, but not Guix/Nix hash-prefix machinery exactly
+
+Fruix still uses immutable store paths under:
+
+- `/frx/store`
+
+and it still treats a store path as a deployment identity boundary.
+
+But Fruix now intentionally differs from Guix/Nix in how the visible store-path prefix is constructed.
+
+Current Fruix policy is:
+
+- centralize store-path naming behind shared helpers
+- hash a small semantic identity record rather than copying Nix's historical path-hash formula exactly
+- include at least:
+  - object kind
+  - logical/display name
+  - output name
+  - payload or manifest identity
+  - hash-scheme version marker
+- truncate the visible SHA-256 prefix to **160 bits**
+- render that visible prefix as **40 hex characters**
+
+Why Fruix does this instead of copying Guix/Nix exactly:
+
+- the main goal was shorter store prefixes, not Nix compatibility for its own sake
+- distinct outputs should have distinct identities because `out`, `lib`, `debug`, and `doc` are semantically different artifacts
+- Fruix wanted one central policy point that can be swapped later without touching every materializer again
+- Fruix did **not** want to inherit Nix's legacy details unless they provide clear value here
+  - custom base32 alphabet and bit ordering
+  - compressed/XOR-folded path hashes
+  - exact historical `output:out` / `source` path-hash conventions
+
+So compared with Guix:
+
+- the important semantic property is the same:
+  - different store objects should get different immutable identities
+- the exact printable prefix algorithm is intentionally simpler in Fruix today
+
+For Guix-familiar operators, the practical takeaway is:
+
+- still think of `/frx/store/...` paths as immutable deployment identities
+- do **not** assume Fruix store prefixes are byte-for-byte comparable to Guix/Nix ones
+- expect Fruix to prefer a simpler, centralized naming policy unless exact Guix/Nix behavior becomes necessary later
+
 ## Where Fruix is intentionally trying to improve on Guix's representation
 
 Fruix is not trying to improve on Guix's core semantics. Guix already got those right.

modules/fruix/system/freebsd/build.scm

@@ -364,11 +364,11 @@
          (cached (hash-ref cache cache-key #f)))
     (if cached
         cached
-        (let* ((hash (sha256-string manifest))
+        (let* ((display-name (string-append (freebsd-package-name prepared-package)
-               (output-path (string-append store-dir "/" hash "-"
-                                           (freebsd-package-name prepared-package)
                                             "-"
-                                           (freebsd-package-version prepared-package))))
+                                            (freebsd-package-version prepared-package)))
+               (output-path (make-store-path store-dir display-name manifest
+                                             #:kind 'freebsd-package)))
           (unless (file-exists? output-path)
             (case (freebsd-package-build-system prepared-package)
               ((copy-build-system)
@@ -454,8 +454,9 @@
 
 (define* (materialize-prefix source-path name version store-dir #:key (extra-files '()))
   (let* ((manifest (prefix-manifest-string source-path extra-files))
-         (hash (sha256-string manifest))
+         (display-name (string-append name "-" version))
-         (output-path (string-append store-dir "/" hash "-" name "-" version)))
+         (output-path (make-store-path store-dir display-name manifest
+                                       #:kind 'prefix)))
     (unless (file-exists? output-path)
       (mkdir-p output-path)
       (for-each (lambda (entry)

modules/fruix/system/freebsd/media.scm

@@ -172,9 +172,10 @@
                                  "\n")
                     "\nreferences=\n"
                     (string-join references "\n")))
-         (hash (sha256-string manifest))
+         (display-name (string-append "fruix-system-"
-         (closure-path (string-append store-dir "/" hash "-fruix-system-"
+                                      (operating-system-host-name os)))
-                                      (operating-system-host-name os))))
+         (closure-path (make-store-path store-dir display-name manifest
+                                        #:kind 'operating-system)))
     (unless (file-exists? closure-path)
       (mkdir-p closure-path)
       (mkdir-p (string-append closure-path "/boot/kernel"))
@@ -870,9 +871,10 @@
                     "\nstore-items=\n"
                     (string-join store-items "\n")
                     "\n"))
-         (hash (sha256-string manifest))
+         (display-name (string-append "fruix-bhyve-image-"
-         (image-store-path (string-append store-dir "/" hash "-fruix-bhyve-image-"
                                       (operating-system-host-name os)))
+         (image-store-path (make-store-path store-dir display-name manifest
+                                            #:kind 'bhyve-image))
          (disk-image (string-append image-store-path "/disk.img"))
          (esp-image (string-append image-store-path "/esp.img"))
          (root-image (string-append image-store-path "/root.ufs")))
@@ -1024,9 +1026,10 @@
                     "\ninstall-metadata=\n"
                     (object->string install-metadata)
                     "\n"))
-         (hash (sha256-string manifest))
+         (display-name (string-append "fruix-installer-image-"
-         (image-store-path (string-append store-dir "/" hash "-fruix-installer-image-"
                                       (operating-system-host-name installer-os)))
+         (image-store-path (make-store-path store-dir display-name manifest
+                                            #:kind 'installer-image))
          (disk-image (string-append image-store-path "/disk.img"))
          (esp-image (string-append image-store-path "/esp.img"))
          (root-image (string-append image-store-path "/root.ufs")))
@@ -1329,9 +1332,10 @@
                     "\ninstall-metadata=\n"
                     (object->string install-metadata)
                     "\n"))
-         (hash (sha256-string manifest))
+         (display-name (string-append "fruix-installer-iso-"
-         (iso-store-path (string-append store-dir "/" hash "-fruix-installer-iso-"
                                       (operating-system-host-name installer-os)))
+         (iso-store-path (make-store-path store-dir display-name manifest
+                                          #:kind 'installer-iso))
          (iso-image (string-append iso-store-path "/installer.iso"))
          (boot-efi-image (string-append iso-store-path "/efiboot.img"))
          (root-image (string-append iso-store-path "/root.img")))

modules/fruix/system/freebsd/source.scm

@@ -150,9 +150,10 @@
          (effective-source (assoc-ref resolution 'effective-source))
          (identity (assoc-ref resolution 'identity))
          (manifest (freebsd-source-manifest source effective-source identity))
-         (hash (sha256-string manifest))
+         (display-name (string-append "freebsd-source-"
-         (output-path (string-append store-dir "/" hash "-freebsd-source-"
                                       (safe-name-fragment (freebsd-source-name source))))
+         (output-path (make-store-path store-dir display-name manifest
+                                       #:kind 'freebsd-source))
          (info-file (string-append output-path "/.freebsd-source-info.scm"))
          (cache-path (assoc-ref resolution 'cache-path))
          (populate-tree (assoc-ref resolution 'populate-tree)))

modules/fruix/system/freebsd/utils.scm

@@ -14,6 +14,8 @@
             safe-command-output
             write-file
             sha256-string
+            store-hash-string
+            make-store-path
             file-hash
             directory-entries
             path-signature
@@ -68,6 +70,40 @@
     (write-file tmp text)
     (command-output "sha256" "-q" tmp)))
 
+(define store-hash-visible-length 40)
+(define store-hash-scheme-version "1")
+
+(define (store-identity-field value)
+  (cond ((symbol? value)
+         (symbol->string value))
+        ((string? value)
+         value)
+        (else
+         (object->string value))))
+
+(define* (store-hash-string payload #:key (kind 'item) name (output "out"))
+  (let* ((identity `((scheme . "fruix-store-path")
+                     (version . ,store-hash-scheme-version)
+                     (kind . ,(store-identity-field kind))
+                     (name . ,(store-identity-field (or name "")))
+                     (output . ,(store-identity-field output))
+                     (payload . ,payload)))
+         (digest (sha256-string (object->string identity))))
+    (string-take digest store-hash-visible-length)))
+
+(define* (make-store-path store-dir display-name payload
+                          #:key
+                          (kind 'item)
+                          name
+                          (output "out"))
+  (string-append store-dir "/"
+                 (store-hash-string payload
+                                    #:kind kind
+                                    #:name (or name display-name)
+                                    #:output output)
+                 "-"
+                 display-name))
+
 (define (file-hash path)
   (command-output "sha256" "-q" path))