[Fix] use command to bypass curl/wget shell functions and aliases

zsh (and interactive bash with `expand_aliases`) bakes a preexisting `curl` alias into nvm's function bodies at source time,
and shell functions named `curl`/`wget` shadow the binaries at call time - either one breaks downloads.
Prefixing invocations with `command` bypasses both: here, `nvm_download`'s dispatch, `nvm_curl_version`, `nvm_curl_libz_support`, and the wget branch of `nvm_get_latest`;
the remaining bare `curl` invocations in `nvm_get_latest` and the install script are prefixed in a followup commit.

The tests that previously mocked curl/wget as shell functions now install fake executables on PATH instead,
via a shared `make_fake_curl` helper in `test/common.sh`,
and a new test asserts the bypass.

Refs #2923

test/slow/nvm_get_latest/nvm_get_latest

@@ -2,37 +2,45 @@
 
 die () { echo "$@" ; cleanup ; exit 1; }
 
+WORK="$PWD/nvm_get_latest-work.$$"
+TEST_BIN="$WORK/bin"
+
 cleanup() {
-  unset -f curl wget nvm_has
+  rm -rf "$WORK"
+  export PATH="$OLDPATH"
 }
 
 \. ../../../nvm.sh
 
+\. ../../common.sh
+
+OLDPATH="$PATH"
+
 EXPECTED_VERSION="v12.3.456"
 URL="https://github.com/nvm-sh/nvm/releases/tag/$EXPECTED_VERSION"
 EXPECTED_CURL_ARGS="--compressed -q -w %{url_effective}\n -L -s -S https://latest.nvm.sh -o /dev/null"
 EXPECTED_WGET_ARGS="-q https://latest.nvm.sh --server-response -O /dev/null"
+export URL EXPECTED_CURL_ARGS EXPECTED_WGET_ARGS
 
-curl() {
-  if [ $# -eq 1 ] && [ "$1" = "-V" ]; then
-    echo "
+VERSION_MESSAGE="
 curl 7.47.0 (x86_64-pc-linux-gnu) libcurl/7.47.0 GnuTLS/3.4.10 zlib/1.2.8 libidn/1.32 librtmp/2.3
 Protocols: dict file ftp ftps gopher http https imap imaps ldap ldaps pop3 pop3s rtmp rtsp smb smbs smtp smtps telnet tftp
 Features: AsynchDNS IDN IPv6 Largefile GSS-API Kerberos SPNEGO NTLM NTLM_WB SSL libz TLS-SRP UnixSockets"
-  elif [ "_$*" != "_$EXPECTED_CURL_ARGS" ]; then
-    echo >&2 "expected args ($EXPECTED_CURL_ARGS), got ($*)"
-    return 1
-  else
-    echo $URL
-  fi
-}
-wget() {
-  if [ "_$*" != "_$EXPECTED_WGET_ARGS" ]; then
-    echo >&2 "expected args ($EXPECTED_WGET_ARGS), got ($*)"
-    return 1
-  else
-    local WGET_CONTENTS
-    WGET_CONTENTS="
+
+# fake curl/wget: `command curl` bypasses shell functions, so the mocks must be executables on PATH
+make_fake_curl "$TEST_BIN" 'if [ "_$*" != "_$EXPECTED_CURL_ARGS" ]; then
+  echo >&2 "expected args ($EXPECTED_CURL_ARGS), got ($*)"
+  exit 1
+fi
+echo "$URL"'
+
+cat > "$TEST_BIN/wget" <<'OUTER'
+#!/bin/sh
+if [ "_$*" != "_$EXPECTED_WGET_ARGS" ]; then
+  echo >&2 "expected args ($EXPECTED_WGET_ARGS), got ($*)"
+  exit 1
+fi
+cat >&2 <<CONTENTS
   HTTP/1.1 301 Moved Permanently
   Location: https://github.com/nvm-sh/nvm/releases/latest
   Content-Type: text/html; charset=utf-8
@@ -82,15 +90,11 @@ wget() {
   X-Content-Type-Options: nosniff
   Vary: Accept-Encoding
   X-Served-By: 926b734ea1992f8ee1f88ab967a93dac
-"
-    "$WGET_CONTENTS" | while read line
-    do
-      >&2 echo "$line"
-    done
-  fi
-}
+CONTENTS
+OUTER
+chmod +x "$TEST_BIN/wget"
 
-\. ../../common.sh
+export PATH="$TEST_BIN:$OLDPATH"
 
 try nvm_get_latest
 [ "_$CAPTURED_STDOUT" = "_$EXPECTED_VERSION" ] \

test/slow/nvm_get_latest/nvm_get_latest failed redirect

@@ -2,20 +2,26 @@
 
 die () { echo "$@" ; cleanup ; exit 1; }
 
+WORK="$PWD/nvm_get_latest_failed_redirect-work.$$"
+TEST_BIN="$WORK/bin"
+
 cleanup() {
-  unset -f curl wget
+  rm -rf "$WORK"
+  export PATH="$OLDPATH"
 }
 
 \. ../../../nvm.sh
 
 \. ../../common.sh
 
-curl() {
-  return 1
-}
-wget() {
-  return 1
-}
+OLDPATH="$PATH"
+
+# fake curl/wget: `command curl` bypasses shell functions, so the mocks must be executables on PATH
+make_fake_curl "$TEST_BIN" 'exit 1'
+printf '#!/bin/sh\nexit 1\n' > "$TEST_BIN/wget"
+chmod +x "$TEST_BIN/wget"
+
+export PATH="$TEST_BIN:$OLDPATH"
 
 try_err nvm_get_latest
 [ "_$CAPTURED_STDERR" = "_https://latest.nvm.sh did not redirect to the latest release on GitHub" ] \