dvc: replace pipeline with dag (#3905)

`pipeline list` is no more, it had some very questionable applications
(none to be precise) and was duplicating old `pipeline show` functionality.
We might introduce a different command to assist in listing (e.g. for
shell completion) in the future.

New `dvc dag` replaces `dvc pipeline show` and by-default will show
all pipelines in the project in ASCII (so there is no more --ascii)
and also `--dot` support, just like before. When given a target,
`dvc dag` (in any mode) will show DAG that leads to the target,
skipping the descendants, unless `--full` is specified.

scripts/completion/dvc.bash

@@ -4,9 +4,10 @@
 #   - https://opensource.com/article/18/3/creating-bash-completion-script
 #   - https://stackoverflow.com/questions/12933362
 
-_dvc_commands='add cache checkout commit config destroy diff fetch freeze get-url get gc \
-  import-url import init install list metrics move params pipeline plots pull push \
-  remote remove repro root run status unfreeze unprotect update version'
+_dvc_commands='add cache checkout commit config dag destroy diff fetch freeze \
+  get-url get gc import-url import init install list metrics move params \
+  plots pull push remote remove repro root run status unfreeze unprotect \
+  update version'
 
 _dvc_options='-h --help -V --version'
 _dvc_global_options='-h --help -q --quiet -v --verbose'
@@ -20,6 +21,8 @@ _dvc_checkout_COMPGEN=_dvc_compgen_DVCFiles
 _dvc_commit='-f --force -d --with-deps -R --recursive'
 _dvc_commit_COMPGEN=_dvc_compgen_DVCFiles
 _dvc_config='-u --unset --local --system --global'
+_dvc_dag='--dot --full'
+_dvc_dag_COMPGEN=_dvc_compgen_DVCFiles
 _dvc_destroy='-f --force'
 _dvc_diff='-t --show-json --show-hash --show-md'
 _dvc_fetch='-j --jobs -r --remote -a --all-branches -T --all-tags -d --with-deps -R --recursive'
@@ -49,10 +52,6 @@ _dvc_move=''
 _dvc_move_COMPGEN=_dvc_compgen_files
 _dvc_params='diff'
 _dvc_params_diff='--all --show-json --show-md --no-path'
-_dvc_pipeline='list show'
-_dvc_pipeline_list=''
-_dvc_pipeline_show='-c --commands -o --outs --ascii --dot --tree -l --locked'
-_dvc_pipeline_show_COMPGEN=_dvc_compgen_DVCFiles
 _dvc_plots='show diff'
 _dvc_plots_show='-t --template -o --out -x -y --show-json --no-csv-header --title --xlab --ylab'
 _dvc_plots_diff='-t --template --targets -o --out -x -y --show-json --no-csv-header --title --xlab --ylab'

scripts/completion/dvc.zsh

@@ -17,6 +17,7 @@ _dvc_commands() {
     "checkout:Checkout data files from cache."
     "commit:Save changed data to cache and update DVC-files."
     "config:Get or set config settings."
+    "dag:Visualize DVC project DAG."
     "destroy:Remove DVC-files, local DVC config and data cache."
     "diff:Show added, modified, or deleted data between commits in the DVC repository, or between a commit and the workspace."
     "fetch:Get files or directories tracked by DVC from remote storage into the cache."
@@ -32,7 +33,6 @@ _dvc_commands() {
     "metrics:Commands to add, manage, collect and display metrics."
     "move:Rename or move a DVC controlled data file or a directory."
     "params:Commands to display params."
-    "pipeline:Manage pipelines."
     "pull:Pull data files from a DVC remote storage."
     "push:Push data files to a DVC remote storage."
     "plots:Generate plot for metrics structured as JSON, CSV or TSV."
@@ -96,6 +96,12 @@ _dvc_config=(
   {-u,--unset}"[Unset option.]"
 )
 
+_dvc_dag=(
+  "--dot[Print DAG in DOT format.]"
+  "--full[Show full DAG that the target belongs too, instead of showing DAG consisting only of ancestors.]"
+  "1:Stage:"
+)
+
 _dvc_destroy=(
   {-f,--force}"[Force destruction.]"
 )
@@ -188,10 +194,6 @@ _dvc_params=(
   "1:Sub command:(diff)"
 )
 
-_dvc_pipeline=(
-  "1:Sub command:(show list)"
-)
-
 _dvc_pull=(
   {-j,--jobs}"[Number of jobs to run simultaneously.]:Number of jobs:"
   {-r,--remote}"[Remote repository to pull from.]:Remote repository:"
@@ -305,6 +307,7 @@ case $words[1] in
   checkout) _arguments $_dvc_global_options $_dvc_checkout ;;
   commit) _arguments $_dvc_global_options $_dvc_commit ;;
   config) _arguments $_dvc_global_options $_dvc_config ;;
+  dag) _arguments $_dvc_global_options $_dvc_dag ;;
   destroy) _arguments $_dvc_global_options $_dvc_destroy ;;
   diff) _arguments $_dvc_global_options $_dvc_diff ;;
   fetch) _arguments $_dvc_global_options $_dvc_fetch ;;
@@ -320,7 +323,6 @@ case $words[1] in
   metrics) _arguments $_dvc_global_options $_dvc_metrics ;;
   move) _arguments $_dvc_global_options $_dvc_move ;;
   params) _arguments $_dvc_global_options $_dvc_params ;;
-  pipeline) _arguments $_dvc_global_options $_dvc_pipeline ;;
   pull) _arguments $_dvc_global_options $_dvc_pull ;;
   push) _arguments $_dvc_global_options $_dvc_push ;;
   plots) _arguments $_dvc_global_options $_dvc_plots ;;