config: add report/compact_output_cols to control which columns to compact in report output

The new report/compact_output_cols setting has exactly the same effect
as report/compact_output setting. The difference is that with the new
setting it's possible to define which cols should be compacted exactly
in contrast to all cols in case of report/compact_output.

In case both compact_output and compact_output_cols is enabled/set,
the compact_output prevails.

For example:

$ lvmconfig --type full report/compact_output report/compact_output_cols
compact_output=0
compact_output_cols=""

$ lvs vg
  LV    VG   Attr       LSize Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  lvol0 vg   -wi-a----- 4.00m

---

$ lvmconfig --type full report/compact_output report/compact_output_cols
compact_output=0
compact_output_cols="data_percent,metadata_percent,pool_lv,move_pv,origin"

$ lvs vg
  LV    VG   Attr       LSize Log Cpy%Sync Convert
  lvol0 vg   -wi-a----- 4.00m

---

$ lvmconfig --type full report/compact_output report/compact_output_cols
compact_output=1
compact_output_cols="data_percent,metadata_percent,pool_lv,move_pv,origin"

$ lvs vg
  LV    VG   Attr       LSize
  lvol0 vg   -wi-a----- 4.00m

1 files changed, 9 insertions, 0 deletions

diff --git a/conf/example.conf.in b/conf/example.conf.in
index c0afcb765..e1afed6f0 100644
--- a/conf/example.conf.in
+++ b/conf/example.conf.in
@@ -1501,6 +1501,15 @@ activation {
 	# This configuration option has an automatic default value.
 	# compact_output = 0
 
+	# Configuration option report/compact_output_cols.
+	# Do not print empty values for given report fields.
+	# The same as compact_output setting, but the compaction is not done
+	# globally for all fields in report but only for given fields. If both
+	# compact_output and compact_output_fields is used at the same time,
+	# the compact_output setting prevails.
+	# This configuration option has an automatic default value.
+	# compact_output_cols = ""
+
 	# Configuration option report/aligned.
 	# Align columns in report output.
 	# This configuration option has an automatic default value.