mavparm: honour use_tabs for params present in only one file

[azrabano23]

What was wrong

mavparmdiff.py -t is documented as "use tabs delimiter between columns for the output", but only the header row and the rows for parameters that differ between the two files were tab-delimited. Parameters present in only one file were still printed with the fixed-width, space-padded format, so the output could not be imported into a spreadsheet (issue #796).

With two three-line parameter files (cat -vt shows tabs as ^I):

$ mavparmdiff.py -t p1.parm p2.parm | cat -vt
PARAMETER^IFILE1^IFILE2
ADSB_ENABLE            0.0000
ADSB_TYPE                           0.0000
AHRS_TRIM_X^I-0.0135^I-0.0512

Root cause

In MAVParmDict.diff() the use_tabs flag was only checked in the header branch and in the "value differs" branch. The "only in FILE1" and "only in FILE2" branches always used the %-16.16s %12.4f formats.

The fix

When use_tabs is set, print NAME\tVALUE for params only in FILE1 and NAME\t\tVALUE for params only in FILE2, so the columns line up with the header and the differing-value rows. The space-padded output is unchanged.

$ mavparmdiff.py -t p1.parm p2.parm | cat -vt
PARAMETER^IFILE1^IFILE2
ADSB_ENABLE^I0.0000
ADSB_TYPE^I^I0.0000
AHRS_TRIM_X^I-0.0135^I-0.0512

Verification

Added test_diff_use_tabs in tests/test_mavparm.py, which captures diff(..., use_tabs=True, header=True) output and checks every row is purely tab-delimited. It fails on master (AssertionError on the space-padded rows) and passes with this change.

python3 -m pytest tests/test_mavparm.py -q   # 4 passed
flake8 mavparm.py tests/test_mavparm.py --count --select=E9,F63,F7,F82   # 0

Tested with Python 3.12 on macOS.

Fixes #796

🤖 Generated with Claude Code