I'm trying to use commit c4de15df559410aff0ca6643724e24cddb0ecbbd as
suggested upstream
(https://github.com/Warsow/qfusion/issues/46#issuecomment-592940682) but
git-fetch fails with

--8<---------------cut here---------------start------------->8---
Submodule 'libsrcs' (https://github.com/Warsow/qfusion-libsrcs.git) registered for path 'libsrcs'
Submodule 'third-party/angelscript' (https://github.com/Qfusion/angelscript.git) registered for path 'third-party/angelscript'
Submodule 'third-party/libRocket' (https://github.com/Qfusion/libRocket) registered for path 'third-party/libRocket'
Submodule 'third-party/openal-soft' (https://github.com/Warsow/openal-soft.git) registered for path 'third-party/openal-soft'
Submodule 'third-party/recastnavigation' (https://github.com/Warsow/recastnavigation.git) registered for path 'third-party/recastnavigation'
Submodule 'third-party/sqlite-amalgamation' (https://github.com/Warsow/sqlite-amalgamation.git) registered for path 'third-party/sqlite-amalgamation'
Cloning into '/gnu/store/l4bjqp1yjkx0hczz0y2i9h0gzayfdx11-warsow-qfusion-2.5-1.c4de15d-checkout/libsrcs'...
Cloning into '/gnu/store/l4bjqp1yjkx0hczz0y2i9h0gzayfdx11-warsow-qfusion-2.5-1.c4de15d-checkout/third-party/angelscript'...
Cloning into '/gnu/store/l4bjqp1yjkx0hczz0y2i9h0gzayfdx11-warsow-qfusion-2.5-1.c4de15d-checkout/third-party/libRocket'...
Cloning into '/gnu/store/l4bjqp1yjkx0hczz0y2i9h0gzayfdx11-warsow-qfusion-2.5-1.c4de15d-checkout/third-party/openal-soft'...
Cloning into '/gnu/store/l4bjqp1yjkx0hczz0y2i9h0gzayfdx11-warsow-qfusion-2.5-1.c4de15d-checkout/third-party/recastnavigation'...
Cloning into '/gnu/store/l4bjqp1yjkx0hczz0y2i9h0gzayfdx11-warsow-qfusion-2.5-1.c4de15d-checkout/third-party/sqlite-amalgamation'...
Submodule path 'libsrcs': checked out 'd3c01feeed14aa2f24c1839fedfb43b4c38a3412'
Submodule path 'third-party/angelscript': checked out '478944145ce6d278abc2a119355c425b332482df'
error: Server does not allow request for unadvertised object 867fc72f980b40325c35d2a9182f741e8e0ca876
Fetched in submodule path 'third-party/libRocket', but it did not contain 867fc72f980b40325c35d2a9182f741e8e0ca876. Direct fetching of that commit failed.
git-fetch: '/gnu/store/zm51w1zv9zchx3n3xjw81zrjnlaswawa-git-minimal-2.25.1/bin/git submodule update --init --recursive' failed with exit code 1
--8<---------------cut here---------------end--------------->8---

Indeed, 867fc72f980b40325c35d2a9182f741e8e0ca876 does not exist in
libRocket, so I suspect it was removed, but isn't Git supposed to fetch
master?  Where did it guess this commit from.  I don't understand how
this is possible.  The .gitmodules file is

--8<---------------cut here---------------start------------->8---
[submodule "third-party/libRocket"]
	path = third-party/libRocket
	url = https://github.com/Qfusion/libRocket
[submodule "third-party/angelscript"]
	path = third-party/angelscript
	url = https://github.com/Qfusion/angelscript.git
[submodule "third-party/recastnavigation"]
	path = third-party/recastnavigation
	url = https://github.com/Warsow/recastnavigation.git
[submodule "third-party/openal-soft"]
	path = third-party/openal-soft
	url = https://github.com/Warsow/openal-soft.git
[submodule "third-party/sqlite-amalgamation"]
	path = third-party/sqlite-amalgamation
	url = https://github.com/Warsow/sqlite-amalgamation.git
[submodule "libsrcs"]
	path = libsrcs
	url = https://github.com/Warsow/qfusion-libsrcs.git
--8<---------------cut here---------------end--------------->8---

and

--8<---------------cut here---------------start------------->8---
> git submodule status --recursive
 d3c01feeed14aa2f24c1839fedfb43b4c38a3412 libsrcs (d3c01fe)
 478944145ce6d278abc2a119355c425b332482df third-party/angelscript (heads/master)
+4889e4c100920cbd0fc9004566d6380771bd77a7 third-party/libRocket (release-1.2.1-1264-g4889e4c1)
 6761218e51699f46bf25c377e65b3e9ea5e434b9 third-party/openal-soft (openal-soft-1.18.1-694-g6761218e)
 2c85309280dbc9c82029e7ab16dfb01b9235c74e third-party/recastnavigation (1.5.0-78-g2c85309)
 bc1dd8284590b5092a9bed4deb80a49e01cfb911 third-party/sqlite-amalgamation (heads/master)
--8<---------------cut here---------------end--------------->8---

I must be missing something about Git submodules...

-- 
Pierre Neidhardt
https://ambrevar.xyz/