From 7347adb8756431709a48fb68136ee703308a4674 Mon Sep 17 00:00:00 2001
From: lemoer <git@irrelefant.net>
Date: Mon, 20 Sep 2021 22:57:42 +0200
Subject: [PATCH] gluon-core: allow overriding gluon-version by .scmversion

Usually gluon calls "git describe" inside the gluon directory to determine
the gluon-version. While this is sufficient in most cases, it becomes
insufficient if you have a meta build system, which patches gluon before
building gluon.

It is actually insufficient, because if you patch gluon before building
it, the the output of "git describe" would then describe the patched
revision and not the base revision (before patching gluon).

After this commit, you can use .scmversion to avoid this problem. By
writing to .scmversion inside the gluon directory before calling make,
gluon will now use the contents of .scmversion instead of "git describe"
to define the gluon-version. So you can write to .scmversion to define
gluon-version before patching gluon in your meta build system.

To do this, you can do something like this in your meta build system:

    cd gluon
    make show-describe > .scmversion
    # apply your own patches to gluon
    git am < ...
    # make gluon
    make GLUON_TARGET=...

Instead of using the output of "make show-describe" as .scmversion, you
can also use any other useful version description. E.g. you may append
the number of additional patches on top of the base commit of gluon (or
so).

As a side note, inside gluon, you can obtain the version (as before) via:

    root@platzhalter-525400123457:/# cat /lib/gluon/gluon-version
    v2021.1-150-gb39ea759+

    root@platzhalter-525400123457:/# gluon-neighbour-info -r nodeinfo
    {
      ...
      "software": {
        "firmware": {
          "base": "gluon-v2021.1-150-gb39ea759+",
          ...
        }
      }
    }

    root@platzhalter-525400123457:/# opkg info gluon-core | grep ^Version:
    Version: v2021.1-150-gb39ea759+
---
 Makefile                    | 5 +++++
 package/gluon-core/Makefile | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index b49ebe80..9ea14406 100644
--- a/Makefile
+++ b/Makefile
@@ -75,6 +75,11 @@ GLUON_ENV = $(foreach var,$(GLUON_VARS),$(var)=$(call escape,$($(var))))
 show-release:
 	@echo '$(GLUON_RELEASE)'
 
+show-version:
+	@cat .scmversion 2>/dev/null || git describe --always --dirty=+ 2>/dev/null || echo unknown
+
+show-describe:
+	@git describe --always --dirty=+ 2>/dev/null || echo unknown
 
 update: FORCE
 	@
diff --git a/package/gluon-core/Makefile b/package/gluon-core/Makefile
index 764affb7..56f3ea1e 100644
--- a/package/gluon-core/Makefile
+++ b/package/gluon-core/Makefile
@@ -2,7 +2,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=gluon-core
 
-GLUON_VERSION = $(shell git describe --always --dirty=+ 2>/dev/null || echo unknown)
+GLUON_VERSION = $(shell cat $(TOPDIR)/../.scmversion 2>/dev/null || git describe --always --dirty=+ 2>/dev/null || echo unknown)
 PKG_VERSION:=$(if $(DUMP),x,$(GLUON_VERSION))
 
 PKG_BUILD_DIR := $(BUILD_DIR)/$(PKG_NAME)