fix: fix install script informational echo's

[WimYedema]

The resolve_source function echo's a return value but also informational messages. I created an info function for the informational messages such that the return value is not muddied. For completeness-sake I also added an error function.

[Copilot]

🟡 Changes recommended

The new info()/error() helpers use echo, which is not fully portable in POSIX /bin/sh for option-like leading arguments (e.g., --prefix), so switching to printf would avoid inconsistent behavior across shells.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR refactors dstack/scripts/install.sh output so resolve_source() can safely return a checkout path on stdout without being interleaved with informational/status messages.

Changes:

• Introduces info() (stderr) and error() (stderr with error: prefix) helper functions.
• Replaces direct echo "error: ..." sites with error ..., and routes resolve_source() progress messages through info ....

File summaries

File	Description
dstack/scripts/install.sh	Adds info/error helpers and uses them to keep resolve_source() stdout clean for its return value.

Review details

Suppressed comments (1)

dstack/scripts/install.sh:66

• Same portability concern as info(): echo has implementation-defined behavior for leading - arguments. Use printf here too so option-like messages (e.g., --repo ...) are never misinterpreted.

error() {
    echo "error: $*" >&2
}

• Files reviewed: 1/1 changed files
• Comments generated: 1
• Review effort level: Lite

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[kvinwang]

Pushed a follow-up commit to this branch (9e1b99d) — hope you don't mind, maintainerCanModify was on.

The stdout leak isn't only from the script's own echos

resolve_source() returns the checkout path on stdout, so anything written there lands in $checkout. git writes to stdout too:

• git checkout <branch> prints Switched to branch/Already on to stderr, but the branch-tracking line Your branch is up to date with 'origin/next'. to stdout.
• git pull --ff-only prints its Updating ../Fast-forward summary to stdout.

So the branch as submitted still broke, including on the default curl | sh path (--ref defaults to the next branch; a tag/SHA happens to be fine because detached-HEAD messages all go to stderr):

$ sh install.sh --src /tmp/e2esrc --repo ... --ref next --prefix ... --no-sudo
cloning dstack source into /tmp/e2esrc
Cloning into '/tmp/e2esrc'...
Already on 'next'
building dstackup from Your branch is up to date with 'origin/next'.
/tmp/e2esrc
install.sh: 268: cd: can't cd to Your branch is up to date with 'origin/next'.
/tmp/e2esrc
exit=2

The fix redirects the git subshells and the git clones as a whole () >&2) rather than adding -q per command, so a git call added later can't reintroduce the same bug.

Copilot's printf note

Applied — it's a real difference, not just style. Under dash, info "-n" with echo swallows the line entirely:

$ dash -c 'info() { echo "$*" >&2; }; info "-n"; info "-e whatever"'
-e whatever          # "-n" vanished, "-e" consumed as a flag
$ dash -c 'info() { printf "%s\n" "$*" >&2; }; info "-n"; info "-e whatever"'
-n
-e whatever

Also routed building dstackup from ... through info for consistency; the final install summary stays on stdout.

Verification

Harness that truncates the script after resolve_source() and checks that stdout is exactly the path, across all six resolution paths:

Test	base (pre-PR)	this PR before	after
temp clone (curl | sh)	FAIL	FAIL	PASS
--src fresh clone	FAIL	FAIL	PASS
--src update (git pull)	FAIL	FAIL	PASS
--src --ref <tag>	FAIL	PASS	PASS
cwd is a checkout	PASS	PASS	PASS
script_checkout via $0	PASS	PASS	PASS

Plus a full end-to-end run with a stubbed cargo (clone → build → install_bin → summary): exits 0, binary installed, stdout carries only the final summary, all progress on stderr. prek run --from-ref <base> --to-ref HEAD passes, shellcheck included.