I grabbed https://common-lisp.net/project/asdf/asdf.tar.gz. It has the following contents:
build/asdf.lisp
.gitattributes
.gitignore
.gitmodules
Makefile
README.md
TODO
action.lisp
asdf.asd
backward-interface.lisp
backward-internals.lisp
bin/asdf-builder
build.xcvb
bundle.lisp
cache.lisp
component.lisp
concatenate-source.lisp
contrib/debug.lisp
contrib/detect-multiply-used-files.lisp
contrib/fasl-op.lisp
contrib/fast-compile-op.lisp
contrib/wild-modules.lisp
debian/README.Debian
debian/README.building
debian/changelog
debian/cl-asdf.dirs
debian/cl-asdf.doc-base
debian/cl-asdf.docs
debian/cl-asdf.examples
debian/cl-asdf.info
debian/cl-asdf.install
debian/cl-asdf.postinst
debian/compat
debian/control
debian/copyright
debian/rules
debian/source/format
debian/watch
doc/.htaccess
doc/Makefile
doc/asdf.texinfo
doc/cclan.png
doc/exported-functions
doc/exported-non-function-names
doc/favicon.ico
doc/index.html
doc/lisp-logo120x80.png
doc/style.css
doc/undocumented-functions
ext/alexandria/
ext/alexandria/.boring
ext/alexandria/.git
ext/alexandria/.gitignore
ext/alexandria/alexandria-tests.asd
ext/alexandria/alexandria.asd
ext/alexandria/arrays.lisp
ext/alexandria/AUTHORS
ext/alexandria/binding.lisp
ext/alexandria/conditions.lisp
ext/alexandria/control-flow.lisp
ext/alexandria/definitions.lisp
ext/alexandria/doc/
ext/alexandria/doc/.gitignore
ext/alexandria/doc/alexandria.texinfo
ext/alexandria/doc/docstrings.lisp
ext/alexandria/doc/Makefile
ext/alexandria/features.lisp
ext/alexandria/functions.lisp
ext/alexandria/hash-tables.lisp
ext/alexandria/io.lisp
ext/alexandria/LICENCE
ext/alexandria/lists.lisp
ext/alexandria/macros.lisp
ext/alexandria/numbers.lisp
ext/alexandria/package.lisp
ext/alexandria/README
ext/alexandria/sequences.lisp
ext/alexandria/strings.lisp
ext/alexandria/symbols.lisp
ext/alexandria/tests.lisp
ext/alexandria/types.lisp
ext/asdf-encodings/
ext/cl-ppcre/
ext/cl-ppcre/.git
ext/cl-ppcre/api.lisp
ext/cl-ppcre/CHANGELOG
ext/cl-ppcre/charmap.lisp
ext/cl-ppcre/charset.lisp
ext/cl-ppcre/chartest.lisp
ext/cl-ppcre/cl-ppcre-unicode/
ext/cl-ppcre/cl-ppcre-unicode/packages.lisp
ext/cl-ppcre/cl-ppcre-unicode/resolver.lisp
ext/cl-ppcre/cl-ppcre-unicode.asd
ext/cl-ppcre/cl-ppcre.asd
ext/cl-ppcre/closures.lisp
ext/cl-ppcre/convert.lisp
ext/cl-ppcre/doc/
ext/cl-ppcre/doc/index.html
ext/cl-ppcre/errors.lisp
ext/cl-ppcre/lexer.lisp
ext/cl-ppcre/optimize.lisp
ext/cl-ppcre/packages.lisp
ext/cl-ppcre/parser.lisp
ext/cl-ppcre/README.md
ext/cl-ppcre/regex-class-util.lisp
ext/cl-ppcre/regex-class.lisp
ext/cl-ppcre/repetition-closures.lisp
ext/cl-ppcre/scanner.lisp
ext/cl-ppcre/specials.lisp
ext/cl-ppcre/test/
ext/cl-ppcre/test/packages.lisp
ext/cl-ppcre/test/perl-tests.lisp
ext/cl-ppcre/test/perltest.pl
ext/cl-ppcre/test/perltestdata
ext/cl-ppcre/test/perltestinput
ext/cl-ppcre/test/simple
ext/cl-ppcre/test/tests.lisp
ext/cl-ppcre/test/unicode-tests.lisp
ext/cl-ppcre/test/unicodetestdata
ext/cl-ppcre/util.lisp
ext/closer-closer-mop/
ext/closer-closer-mop/.git
ext/closer-closer-mop/closer-abcl.lisp
ext/closer-closer-mop/closer-allegro.lisp
ext/closer-closer-mop/closer-clisp.lisp
ext/closer-closer-mop/closer-clozure.lisp
ext/closer-closer-mop/closer-cmu.lisp
ext/closer-closer-mop/closer-ecl.lisp
ext/closer-closer-mop/closer-lispworks.lisp
ext/closer-closer-mop/closer-mcl.lisp
ext/closer-closer-mop/closer-mop-packages.lisp
ext/closer-closer-mop/closer-mop-shared.lisp
ext/closer-closer-mop/closer-mop-system.cl
ext/closer-closer-mop/closer-mop.asd
ext/closer-closer-mop/closer-sbcl.lisp
ext/closer-closer-mop/closer-scl.lisp
ext/closer-closer-mop/features.lisp
ext/closer-closer-mop/features.txt
ext/closer-closer-mop/supported-cls.txt
ext/fare-mop/
ext/fare-mop/.git
ext/fare-mop/.gitignore
ext/fare-mop/build.xcvb
ext/fare-mop/fare-mop.asd
ext/fare-mop/package.lisp
ext/fare-mop/README
ext/fare-mop/utilities.lisp
ext/fare-quasiquote/
ext/fare-quasiquote/.git
ext/fare-quasiquote/build.xcvb
ext/fare-quasiquote/fare-quasiquote-extras.asd
ext/fare-quasiquote/fare-quasiquote-matcher.asd
ext/fare-quasiquote/fare-quasiquote-matcher.lisp
ext/fare-quasiquote/fare-quasiquote-optima.asd
ext/fare-quasiquote/fare-quasiquote-optima.lisp
ext/fare-quasiquote/fare-quasiquote-readtable.asd
ext/fare-quasiquote/fare-quasiquote-test.asd
ext/fare-quasiquote/fare-quasiquote.asd
ext/fare-quasiquote/packages.lisp
ext/fare-quasiquote/pp-quasiquote.lisp
ext/fare-quasiquote/quasiquote-readtable.lisp
ext/fare-quasiquote/quasiquote-test.lisp
ext/fare-quasiquote/quasiquote.lisp
ext/fare-quasiquote/README
ext/fare-utils/
ext/fare-utils/.git
ext/fare-utils/.gitignore
ext/fare-utils/base/
ext/fare-utils/base/hash-tables.lisp
ext/fare-utils/base/lists.lisp
ext/fare-utils/base/macros.lisp
ext/fare-utils/base/more-strings.lisp
ext/fare-utils/base/objects.lisp
ext/fare-utils/base/packages.lisp
ext/fare-utils/base/parse-cl-syntax.lisp
ext/fare-utils/base/streams.lisp
ext/fare-utils/base/strings.lisp
ext/fare-utils/base/symbols.lisp
ext/fare-utils/base/utils.lisp
ext/fare-utils/build.xcvb
ext/fare-utils/fare-utils.asd
ext/fare-utils/filesystem/
ext/fare-utils/filesystem/atomic.lisp
ext/fare-utils/filesystem/files.lisp
ext/fare-utils/filesystem/pathnames.lisp
ext/fare-utils/package.lisp
ext/fare-utils/README
ext/fare-utils/stateful/
ext/fare-utils/stateful/binary-heap.lisp
ext/fare-utils/stateful/binomial-heap.lisp
ext/fare-utils/stateful/container.lisp
ext/fare-utils/stateful/dllist.lisp
ext/fare-utils/stateful/iterator.lisp
ext/fare-utils/stateful/package.lisp
ext/fare-utils/stateful/sorting.lisp
ext/fare-utils/test/
ext/fare-utils/test/build.xcvb
ext/fare-utils/test/fare-utils-test.asd
ext/fare-utils/test/package.lisp
ext/fare-utils/test/strings.lisp
ext/fare-utils/TODO
ext/inferior-shell/
ext/inferior-shell/.git
ext/inferior-shell/build.xcvb
ext/inferior-shell/host.lisp
ext/inferior-shell/inferior-shell-test.asd
ext/inferior-shell/inferior-shell.asd
ext/inferior-shell/LICENSE
ext/inferior-shell/macros.lisp
ext/inferior-shell/pkgdcl.lisp
ext/inferior-shell/process-spec.lisp
ext/inferior-shell/README
ext/inferior-shell/run-generic.lisp
ext/inferior-shell/run-sbcl.lisp
ext/inferior-shell/run.lisp
ext/inferior-shell/test.lisp
ext/inferior-shell/utilities.lisp
ext/lisp-invocation/
ext/lisp-invocation/.git
ext/lisp-invocation/build.xcvb
ext/lisp-invocation/LICENSE
ext/lisp-invocation/lisp-invocation.asd
ext/lisp-invocation/lisp-invocation.lisp
ext/named-readtables/
ext/named-readtables/.git
ext/named-readtables/.gitignore
ext/named-readtables/cruft.lisp
ext/named-readtables/define-api.lisp
ext/named-readtables/doc/
ext/named-readtables/doc/named-readtables.html
ext/named-readtables/LICENSE
ext/named-readtables/named-readtables.asd
ext/named-readtables/named-readtables.lisp
ext/named-readtables/package.lisp
ext/named-readtables/tests/
ext/named-readtables/tests/package.lisp
ext/named-readtables/tests/rt.lisp
ext/named-readtables/tests/tests.lisp
ext/named-readtables/utils.lisp
ext/optima/
ext/optima/.git
ext/optima/.gitignore
ext/optima/lib/
ext/optima/lib/ppcre.lisp
ext/optima/Makefile
ext/optima/optima.asd
ext/optima/optima.ppcre.asd
ext/optima/optima.test.asd
ext/optima/README.md
ext/optima/src/
ext/optima/src/compiler.lisp
ext/optima/src/extra.lisp
ext/optima/src/fail.lisp
ext/optima/src/match.lisp
ext/optima/src/packages.lisp
ext/optima/src/pattern.lisp
ext/optima/src/runtime.lisp
ext/optima/src/util.lisp
ext/optima/test/
ext/optima/test/suite.lisp
find-component.lisp
find-system.lisp
footer.lisp
header.lisp
interface.lisp
lisp-action.lisp
operate.lisp
operation.lisp
output-translations.lisp
package-inferred-system.lisp
parse-defsystem.lisp
plan.lisp
source-registry.lisp
system.lisp
test/always-error.lisp
test/asdf-pathname-test.script
test/bad-shell-command
test/defmacro-foo.lisp
test/defsetf-foo.lisp
test/defun-foo.lisp
test/defun-setf-foo.lisp
test/dll-test.lisp
test/dll-user.lisp
test/duplicate-components-test.script
test/duplicate-components.asd
test/file1.lisp
test/file2.lisp
test/file3-only.asd
test/file3.lisp
test/file4.lisp
test/good-shell-command
test/graveyard/test-preferences-1.lisp
test/graveyard/test-preferences-1.script
test/graveyard/test-preferences-system-1.asd
test/graveyard/test-preferences-system-load.lisp
test/graveyard/test-preferences-system-test.lisp
test/graveyard/test6.script
test/graveyard/test7.script
test/hello-world-example.asd
test/hello.lisp
test/in-progress.lisp
test/l-file.lisp
test/l-operation.lisp
test/lambda.lisp
test/logical-file.lisp
test/make-hello-world.lisp
test/monodll-1.lisp
test/monodll-user.lisp
test/monodll.lisp
test/package-inferred-system-test.script
test/package-inferred-system-test/a.lisp
test/package-inferred-system-test/a/x.lisp
test/package-inferred-system-test/b.lisp
test/package-inferred-system-test/c.lisp
test/package-inferred-system-test/d.lisp
test/package-inferred-system-test/e.lisp
test/package-inferred-system-test/package-inferred-system-test.asd
test/package-test.lisp
test/run-tests.sh
test/script-support.lisp
test/sources/level1/file1.lisp
test/sources/level1/level2/file2.lisp
test/sources/level1/level2/static.file
test/sources/level1/test-tmp.cl
test/stamp-propagation/file1.lisp
test/stamp-propagation/file2.lisp
test/stamp-propagation/test-stamp-propagation.lisp
test/stderr
test/test-around-compile.script
test/test-asdf.asd
test/test-asdf.script
test/test-builtin-source-file-type.script
test/test-bundle.script
test/test-cache-for-introspection.script
test/test-cache.script
test/test-compile-file-failure.lisp
test/test-compile-file-failure.script
test/test-concatenate-source.lisp
test/test-concatenate-source.script
test/test-configuration.script
test/test-deferred-warnings.script
test/test-defsystem-depends-on.script
test/test-defsystem-errors.script
test/test-encodings.script
test/test-extension.l
test/test-file
test/test-force.script
test/test-inline-methods.script
test/test-logical-pathname.asd
test/test-logical-pathname.script
test/test-macosx.script-ignore
test/test-missing-lisp-file.script
test/test-module-depend.asd
test/test-module-depend.script
test/test-module-excessive-depend.script
test/test-module-pathnames.script
test/test-modules-serial.asd
test/test-modules.asd
test/test-multiple.asd
test/test-multiple.script
test/test-mutual-redefinition-1.asd
test/test-mutual-redefinition-2.asd
test/test-mutual-redefinition.script
test/test-nested-1.lisp
test/test-nested-components.script
test/test-operation-classes.script
test/test-package.asd
test/test-package.script
test/test-program.script
test/test-redundant-recompile.script
test/test-retry-loading-component-1.script
test/test-run-program.script
test/test-samedir-modules.asd
test/test-samedir-modules.script
test/test-source-file-type-1.asd
test/test-source-file-type-2.asd
test/test-source-file-type.script
test/test-stamp-propagation.script
test/test-static-and-serial.script
test/test-sysdef-asdf.script
test/test-system-pathnames.script
test/test-tmp.cl
test/test-tmp.lsp
test/test-touch-system-1.script
test/test-touch-system-2.script
test/test-try-recompiling-1.script
test/test-try-refinding.script
test/test-urls-1.asd
test/test-urls-1.script
test/test-urls-2.asd
test/test-urls-2.script
test/test-utilities.script
test/test-version.script
test/test-weakly-depends-on-present.script
test/test-weakly-depends-on-unpresent.asd
test/test-weakly-depends-on-unpresent.script
test/test-xach-update-bug.script
test/test.lisp
test/test1.asd
test/test1.script
test/test2.asd
test/test2.script
test/test2a.asd
test/test2b1.asd
test/test2b2.asd
test/test2b3.asd
test/test3.asd
test/test3.script
test/test8.script
test/test9-1.asd
test/test9-2.asd
test/test9.script
test/try-recompiling-1.asd
test/try-recompiling-1.lisp
test/try-reloading-1.asd
test/try-reloading-dependency.hidden
test/unintern-foo.lisp
test/use-foo.lisp
test/use-setf-foo.lisp
test/version.lisp-expr
test/wild-module.script
test/xach-foo-1/a.lisp
test/xach-foo-1/test-asdf-location-change.asd
test/xach-foo-2/a.lisp
test/xach-foo-2/b.lisp
test/xach-foo-2/test-asdf-location-change.asd
test/xach-foofail/foofail.lisp
tools/cl-source-registry-cache.lisp
tools/install-asdf.lisp
tools/load-asdf.lisp
uiop/README.md
uiop/asdf-driver.asd
uiop/backward-driver.lisp
uiop/build.xcvb
uiop/common-lisp.lisp
uiop/configuration.lisp
uiop/contrib/debug.lisp
uiop/driver.lisp
uiop/filesystem.lisp
uiop/image.lisp
uiop/lisp-build.lisp
uiop/os.lisp
uiop/package.lisp
uiop/pathname.lisp
uiop/run-program.lisp
uiop/stream.lisp
uiop/uiop.asd
uiop/utility.lisp
uiop/version.lisp-expr
upgrade.lisp
user.lisp
version.lisp-expr
I'd expect these to be in a subdirectory in the tarball, like "asdf-3.1.4/version.lisp-expr", etc.
I fixed the release script in master, and retroactively re-ran it on the 3.1.4 release to re-create a better asdf-3.1.4.tar.gz. Please see that it works for you.
Note that, unhappily, SBCL had a recent incompatible change that breaks 3.1.4, so I also merged the fixes in the minimakefile branch, and produced tarballs for 3.1.4.20, which is our current release candidate for 3.1.5.