completion: Support the DWIM mode for git checkout

Ever since commit 70c9ac2 (DWIM: "git checkout frotz" to "git checkout
-b frotz origin/frotz"), git checkout has supported a DWIM mode where
it creates a local tracking branch for a remote branch if just the name
of the remote branch is specified on the command-line and only one remote
has a branch with that name. Teach the bash completion script to understand
this DWIM mode and provide such remote-tracking branch names as possible
completions.

Signed-off-by: Kevin Ballard <kevin@sb.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index f83f019ca91a2611f5bd3474ccf6d10081320c4c..1c9c125bb03eceeb153854bf2c6003aa382be731 100755 (executable)
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -380,16 +380,19 @@ __git_tags ()
        done
 }
 
-# __git_refs accepts 0 or 1 arguments (to pass to __gitdir)
+# __git_refs accepts 0, 1 (to pass to __gitdir), or 2 arguments
+# presence of 2nd argument means use the guess heuristic employed
+# by checkout for tracking branches
 __git_refs ()
 {
-       local i is_hash=y dir="$(__gitdir "${1-}")"
+       local i is_hash=y dir="$(__gitdir "${1-}")" track="${2-}"
        local cur="${COMP_WORDS[COMP_CWORD]}" format refs
        if [ -d "$dir" ]; then
                case "$cur" in
                refs|refs/*)
                        format="refname"
                        refs="${cur%/*}"
+                       track=""
                        ;;
                *)
                        for i in HEAD FETCH_HEAD ORIG_HEAD MERGE_HEAD; do
@@ -401,6 +404,21 @@ __git_refs ()
                esac
                git --git-dir="$dir" for-each-ref --format="%($format)" \
                        $refs
+               if [ -n "$track" ]; then
+                       # employ the heuristic used by git checkout
+                       # Try to find a remote branch that matches the completion word
+                       # but only output if the branch name is unique
+                       local ref entry
+                       git --git-dir="$dir" for-each-ref --shell --format="ref=%(refname:short)" \
+                               "refs/remotes/" | \
+                       while read entry; do
+                               eval "$entry"
+                               ref="${ref#*/}"
+                               if [[ "$ref" == "$cur"* ]]; then
+                                       echo "$ref"
+                               fi
+                       done | uniq -u
+               fi
                return
        fi
        for i in $(git ls-remote "$dir" 2>/dev/null); do
@@ -988,7 +1006,13 @@ _git_checkout ()
                        "
                ;;
        *)
-               __gitcomp "$(__git_refs)"
+               # check if --track, --no-track, or --no-guess was specified
+               # if so, disable DWIM mode
+               local flags="--track --no-track --no-guess" track=1
+               if [ -n "$(__git_find_on_cmdline "$flags")" ]; then
+                       track=''
+               fi
+               __gitcomp "$(__git_refs '' $track)"
                ;;
        esac
 }