gosalyn: Case 2 design ruling after r11, the sync's askpass helper, fixed argv with followRedirects=false and credential.helper reset, LC_ALL=C, exact Username and Password prompts for the host and user, no userinfo, slot path not fd 3 (row 222, megavolt-0060, dewey-0765, gosalyn-0068, a304dad94)

agents/gosalyn/work/case2/DESIGN.md

@@ -30,6 +30,22 @@ forgery question (mos-1097 item 2, #430) is unchanged, and so is the Console por
 re-pin, but it is still there. The C2-13a brief carries this when Sage re-briefs it into the installer
 row (I2, Vikunja #432).
 
+## Ruling after r11: the sync's askpass helper (row 222)
+
+Before building C2-03a, Megavolt compared 7.2's `GIT_ASKPASS` helper with row 199's credential helper
+(megavolt-0060, asked by sage-1487). As written, 7.2 left three gaps. git's default
+`http.followRedirects=initial` follows a 302 to another host. A helper that prints the token answers any
+prompt, with no host check. And git asks askpass for the username too, so the token went out as the
+username. Dewey (dewey-0765) and I (gosalyn-0068) accepted the fix, and Sage ruled it into the C2-03a brief
+(a304dad94).
+
+The argv is `SAFE`, then `-c protocol.https.allow=always`, `-c http.followRedirects=false` and
+`-c credential.helper=`, then `-C <mirror>`. The env adds `LC_ALL=C`, because the helper matches git's
+prompt text and git translates that text. The helper answers only the exact Username and Password
+prompts for the configured host and user, and exits 1 on anything else. The URL carries no userinfo. The
+helper reads the slot path, so the bus never holds the value, and that is why it doesn't use row 199's
+fd 3. Section 7.2 says so.
+
 ## Changes from r10
 
 Webby returned r10 with B1-B3 and N1-N5 (webby-0036, `agents/webby/work/case2-r10/REVIEW.md` at
@@ -932,9 +948,11 @@ for the agents than in Obsidian. A full-path link avoids that (N4, 1.3).
 ### 7.2 Sync (bus side)
 
 One function, `syncCommand(kind, url)`, builds every fetch (and later push). Its argv is `SAFE`
-(`git.mjs:7-9`), then exactly `-c protocol.https.allow=always`, then `-C <mirror>`, then the command with
+(`git.mjs:7-9`), then `-c protocol.https.allow=always`, `-c http.followRedirects=false` and
-the URL as an argument. Its env is `gitEnv()` plus `GIT_ASKPASS` naming a helper script outside the
+`-c credential.helper=`, then `-C <mirror>`, then the command with the URL as an argument. Its env is
-mirror, which reads the slot file and prints the token. The token is never in the URL, the mirror's
+`gitEnv()` plus `LC_ALL=C` and `GIT_ASKPASS` naming a helper script outside the mirror, which reads the
+slot file. The helper answers only the exact Username and Password prompts for the configured host and
+user and exits 1 on anything else (ruling after r11). The URL carries no userinfo. The token is never in the URL, the mirror's
 config, argv, logs or replies (CONSTITUTION gate 13). The URL must be `https://`. Tests reach a local bare
 repo only through a module parameter that replaces `syncCommand`. No business file field or bus verb can
 reach that parameter.
@@ -957,9 +975,10 @@ more than 60 seconds old.
 Later (C2-03b, with C2-02): push of bus commits, the push race retried once, `unpushed`, and
 `library-remote-invalid` refusals of bus writes (B9).
 
-Tests (C2-03a): `syncCommand` argv equals `SAFE` plus exactly one `protocol.https.allow=always` and no
+Tests (C2-03a): `syncCommand` argv equals `SAFE` plus the fixed sequence above, with no other
-other `protocol.*` key. Its env holds `GIT_ASKPASS` pointing outside the mirror, and the helper prints
+`protocol.*` key. Its env holds `LC_ALL=C` and `GIT_ASKPASS` pointing outside the mirror. The helper
-the slot file's content. A search of argv, the mirror's config and the run log finds no token. Against
+prints the user for the username prompt and the slot file's content for the password prompt, and
+refuses a wrong host, a wrong port and another user. A 302 to another host fails the fetch. A search of argv, the mirror's config and the run log finds no token. Against
 a bare repo: fast-forward, R-problems recorded without holding the head, `library-diverged` kept until
 `--accept`, a failed fetch kept serving. A mutant that sets `protocol.allow=always` fails the argv test.