From 72ed7bd3e95e8222beece3540ef5022b90aa9df5 Mon Sep 17 00:00:00 2001
From: Sebastiaan van Stijn <github@gone.nl>
Date: Wed, 6 Apr 2022 11:06:44 +0200
Subject: [PATCH] scripts/build: fix date formatting on macOS

This was introduced in 9d40c7464eb2a351e8b2e63dd1fdce6a43f2c70f, which added
support for `SOURCE_DATE_EPOCH` to override the build-time.

macOS uses the BSD flavor of `date`, which does not support the `--date` option
to set a custom time.

Before this:

    DISABLE_WARN_OUTSIDE_CONTAINER=1 make binary
    ./scripts/build/binary
    date: illegal option -- -
    usage: date [-jnRu] [-d dst] [-r seconds] [-t west] [-v[+|-]val[ymwdHMS]] ...
    [-f fmt date | [[[mm]dd]HH]MM[[cc]yy][.ss]] [+format]

After this:

    DISABLE_WARN_OUTSIDE_CONTAINER=1 make binary
    ./scripts/build/binary
    Building static docker-darwin-amd64
    + go build -o build/docker-darwin-amd64 -tags ' osusergo pkcs11' -ldflags ' -w -X "github.com/docker/cli/cli/version.GitCommit=a4b6fe16a" -X "github.com/docker/cli/cli/version.BuildTime=2022-04-06T10:57:25Z" -X "github.com/docker/cli/cli/version.Version=20.10.2-589-ga4b6fe16a.m"' -buildmode=pie github.com/docker/cli/cmd/docker
    ...

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
---
 scripts/build/.variables | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/scripts/build/.variables b/scripts/build/.variables
index 76b0602f06..ae2500dfa4 100755
--- a/scripts/build/.variables
+++ b/scripts/build/.variables
@@ -12,7 +12,15 @@ TARGET=${TARGET:-"build"}
 PLATFORM=${PLATFORM:-}
 VERSION=${VERSION:-$(git describe --match 'v[0-9]*' --dirty='.m' --always --tags | sed 's/^v//' 2>/dev/null || echo "unknown-version" )}
 GITCOMMIT=${GITCOMMIT:-$(git rev-parse --short HEAD 2> /dev/null || true)}
-BUILDTIME=${BUILDTIME:-$(date -u --date="@${SOURCE_DATE_EPOCH:-$(date +%s)}" +"%Y-%m-%dT%H:%M:%SZ")}
+
+if [ "$(uname)" = "Darwin" ]; then
+    # Using BSD date (macOS), which doesn't suppoort the --date option
+    # date -jf "<input format>" "<input value>" +"<output format>" (https://unix.stackexchange.com/a/86510)
+    BUILDTIME=${BUILDTIME:-$(date -jf "%s" "${SOURCE_DATE_EPOCH:-$(date +%s)}" +"%Y-%m-%dT%H:%M:%SZ")}
+else
+    # Using GNU date (Linux)
+    BUILDTIME=${BUILDTIME:-$(date -u --date="@${SOURCE_DATE_EPOCH:-$(date +%s)}" +"%Y-%m-%dT%H:%M:%SZ")}
+fi
 
 GOOS="$(go env GOOS)"
 GOARCH="$(go env GOARCH)"