Write list text output to os.Stdout in a single write

[Slach]

Fixes the Test (1.27, 22.3) failure of https://github.com/Altinity/clickhouse-backup/actions/runs/35335959574 (TestEmptyKeyPrefixRetention).

Root cause

PrintBackup in text format renders the tabwriter directly onto os.Stdout. tabwriter.Flush emits every cell and padding run as a separate Write (11 writes per row), zerolog writes to stderr, and under docker exec the daemon copies stdout and stderr from separate pipes with no ordering guarantee. Under CI load a stderr log line landed between the first two cells of a row:

empty_key_prefix_1_22_32026-09-18 10:50:10.499 WRN pkg/storage/general.go:383 > BackupList: skip nameless entry "/" ...
   2026-09-18 10:50:05   remote      all:8.60KiB,...   tar, regular

so (?m)^empty_key_prefix_1_22_3 no longer matched. The splice point is exactly the boundary between tabwriter's write #1 (the name) and write #2 (the padding).

Reproduced locally with 8 parallel docker exec loops of a tiny program doing the same stderr line + chunked stdout row: 1 spliced output in 1200 runs. With the table rendered into a buffer and written once: 0 in 1200.

Fix

Render the table into a bytes.Buffer and write it to os.Stdout in one Write (newStdoutTabWriter), the same approach 4a22d04 applied to json/yaml/csv/tsv in v2.8.1. The second commit applies it to the two other tabwriter sites in list.go (printLiveTableRows, renderTextSection behind tables / list tables), which had the same defect.

Verification

• GOFLAGS= go test ./pkg/backup/: 255 passed
• CLICKHOUSE_VERSION=22.3 RUN_TESTS='^(TestTablesCommand|TestTablesCommandListParts|TestListFormat|TestEmptyKeyPrefixRetention)$' ./test/integration/run.sh: PASS

The second failed job of that run, Test (1.27, 26.3), is unrelated: all integration tests passed and the Report integration coverage step failed because the Coveralls release download returned 504 Gateway Time-out.

🤖 Generated with Claude Code

[coveralls]

Coverage Report for CI Build 35420933277

Coverage at 67.559% (no base build to compare)

Details

• Coverage remained the same as the base build.
• Patch coverage: 5 uncovered changes across 1 file (14 of 19 lines covered, 73.68%).
• No coverage regressions found.

Uncovered Changes

File	Changed	Covered	%
pkg/backup/list.go	19	14	73.68%

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	27086
Covered Lines:	18299
Line Coverage:	67.56%
Coverage Strength:	68815.97 hits per line

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💛 - Coveralls